A Revision of the Stylasteridae (Cnidaria, Hydrozoa, Filifera) from Alaska and Adjacent Waters

Abstract The stylasterid fauna of Alaska is revised, consisting of the description or redescription and illustration of 21 species, one additional subspecies, and a geographically adjacent species: Stylaster venustus. Six new species and one new subspecies are described: Errinopora fisheri, Errinopora undulata, Errinopora disticha, Errinopora dichotoma, Stylaster crassiseptum, Stylaster repandus, and Stylaster parageus columbiensis. Four subspecies are raised to species rank: Stylaster leptostylus, Stylaster trachystomus, Stylaster parageus, and Distichopora japonica, and five species and one subspecies were synonymized. A dichotomous key to the Errinopora species and tabular keys to the Errinopora and Alaskan Stylaster species are provided. The focus of the study was on the stylasterids from Alaska, primarily those from the diverse Aleutian Islands, but also including records from British Columbia. This is the first revisionary work on this fauna since the seminal report by Fisher in 1938.


Introduction
The history of the published information about Alaskan stylasterids is not long. The first stylasterids to be reported from off Alaska were beach-worn specimens or coralla obtained from very shallow water from the Aleutian Islands and the Alaskan Penin- Specimens were studied using scanning electron microscopy using the methodology as described by Cairns (1983). Genomic DNA and 37 new mitochondrial rDNA 16S sequences for the six Errinopora species from Alaska (GenBank accession numbers: JN572403-JN572439) were obtained as described in Lindner et al. (2008), using primers as described in Cunningham and Buss (1993). Sequences were aligned using ClustalX (Thompson et al. 1997) and phylogenetic analyses were performed in PAUP* 4.0 (Swofford 1999). Morphological terms used herein are defined in Cairns (2011), and the term pseudocyclosystem is defined as a cyclosystem-like structure (composed of a gastropore surrounded by dactylopores) that may be found at basal branches of some stylasterid species, and in which the dactylopores are usually not fused with the central gastropore and may not have the slits (dactylotome) of the dactylopore spines directed towards the central gastropore. In contrast to cyclosystemate stylasterids (e.g., Stylaster, Conopora, Crypthelia), pseudocyclosystemate species (e.g., Errinopora) have this polyp arrangement at basal portions of branches and colonies, and a different polyp arrangement at branch tips.
The specimens on which this study was based resulted from collections from both the United States government and university vessels as well as from privately owned fishing vessels, the latter often having many with colourful names. The US research vessels owned by the US Government are the Albatross and the Miller Freeman, whereas fishing vessels temporarily chartered by the US Government (for NOAA's RACE surveys) included: Dominator, Sea Storm, Pacific Knight, and the Vesteraalen. Additional private fishing vessels included: Alaska Beauty, Alaska Sea, AlaskaTrojan, Alaskan Leader, Ballyhoo, Delta Alfa, North Pacific, Ocean Olympic, Patricia Lee, and Shishaldin. Additionaly, the manned submersible Delta and the Remotely Operated Vehicles Jason II Alb-4781 (USNM 76375). Type locality. Alb-3480: 52°06'00"N, 171°45'00"W (Amukta Pass, Aleutian Islands), 518 m.
Pore rows well defined (Fig. 2B), 1.0-1.3 mm in width, and restricted to lateral branch edges, although isolated rows and some irregularities may occur proximally on large colonies. Gastropores linearly arranged in a shallow sulcus, closely spaced (approximately 12-16 per cm), and circular in shape, measuring 0.33-0.41 mm in diameter. Gastropore tubes long and slightly curved, a diffuse ring palisade present near gastrostyle tip, the elements globular and about 30 µm in diameter; tabulae absent. Gastrostyles long, slender, and fragile, up to 1 mm in length and 0.09 mm in diameter, having high H:W ratios up to 8-10. Gastrostyles longitudinally ridged and bear numerous long slender spines up to 0.07 mm in length and 10-12 µm in diameter. U-shaped dactylopore spines arranged on both sides of gastropore row, but often more common on one side than the other, e.g., 18-20 dactylopore spines on one side opposite 28-40 spines on other side. Dactylopore spines up to 0.4 mm tall and 0.25-0.30 mm in width, with a dactylotome width of 0.07-0.08 mm, always directed toward or slightly obliquely to the adjacent gastropore. Dactylostyles absent.
Female ampullae (Fig. 2J) prominent, superficial, hemispherical mounds clustered on branch faces, 1.0-1.5 mm in diameter. Ampullae usually covered by low ridges, either radiating from the central apex or arranged in parallel, longitudinal rows aligned with branch axis. Lateral efferent pores 0.25-0.30 mm in diameter. Male ampullae (Fig. 2K) also superficial mounds, but mostly embedded in coenosteum (internal), also occurring in clusters on branch faces. Male ampullae irregular in shape, often with an apical tip, and smaller than female ampullae (0.35-0.45 mm in diameter).
Remarks. Among the 26 Recent species of Distichopora (see Cairns et al. 1999;Cairns 2005;and Appeltans et al. 2011: WoRMS database -www.marinespecies.org), the most similar is Distichopora borealis japonica Broch, 1942, described from Sagami Bay, Japan (110 m). Although similar in gross morphology, subspecies japonica differs in coenosteal texture (porcellaneous), and in ampulla shape, each female ampulla having more than one efferent pore and the male ampullae clustered densely in a continuous mat. Also, the dactylotomes of the dactylopore spines are oriented upward to outward (away from the gastropores), not inward toward the gastropores. These differences would argue for an elevation to the species level of this putative subspecies. The observations are based on examination of a fragment of a syntype of D. borealis japonica (USNM 76868) and additional Japanese material deposited at the NMNH (USNM 44198,44199,44202,and 44217). Of the 111 specimens examined, 45 are female, 53 male, and 13 indeterminate in gender.
Distribution. Common in the Aleutian Islands from the Near Islands to Amukta Pass, including Bowers Bank; off Cape Ommaney, Alexander Archipelago, and Dixon Entrance, Queen Charlotte Islands; 53-1267 m, the shallowest record being from Cape Ommaney.
Discussion. The genus is monotypic. According to the molecular analysis of Lindner et al. (2008) it groups within the Distichopora clade as a sister species of D. borealis. The close relationship to Distichopora was also suggested by Cairns (1991) in the original description of Cyclohelia, both genera having axial gastro-and dactylopores, elongate gastrostyles, and in lacking dactylostyles. Cyclohelia differs only in having non-linear gastro-and dactylopores, internal ampullae, and differently shaped dactylopore spines. The colony morphology of Distichopora anceps Cairns, 1978 is remarkably similar to that of typical Cyclohelia, i.e., lamellar with a cleft dividing the colony into two adjacent undulating fronds. However, large specimens of Cyclohelia tend to form almost entirely lamellate colonies, whereas large specimens of D. anceps remain clearly lamellate-branching (Cairns 2005), rendering the colonies of D. anceps as a "transition" in morphology between the two genera.
Discussion. The ten species in this genus are differentiated and compared in both a dichotomous key (see below) and tabular key ( Table 1); six of them occur exclusively in the Aleutian Islands. Another species was tentatively assigned to this genus by Cairns (1983b), Errinopora lobata (Nielsen, 1919), a Paleocene fossil from Denmark. This species was re-examined by Weidlich (1990, 2005), based on subsequently collected non-type material from the Faske Formation in Denmark. They noted that whereas the dactylopore spines were typical of Errina or Errinopora, the spines did not contain dactylostyles, and thus resembled Errina more than Errinopora. We have examined the holotype of Labiopora lobata Nielsen, 1919 (GM1782), which is a uniplanar colony 10.2 cm tall and 8.0 cm wide, with branches about 0.5 cm in diameter embedded within a Dendrophyllia matrix. The colony has pores, or broken bulges, of three sizes: small and elongate (75-110 µm in width), medium and round to somewhat quadratic (0.3-0.53 mm wide), and large, round or somewhat triangular (up to 1.7 mm). The former are quite shallow and probably the result of a reticulate coenosteal surface, whereas the medium-sized pores are deep and possibly represent the gastropores, one of which has a cyclosystem-like structure 1.9 mm in diameter. The largest pores appear to be ruptured ampullae. None of them, however, resemble dactylopore spines like those reported by Nielsen (1919) or Weidlich (1990, 2005), suggesting that the species reported by the latter authors is neither Errina nor Errinopora. Likewise, the lack of dactylopore spines in the type of L. lobata precludes it from being Errinopora, and thus we currently suggest an incertae sedis placement of this species until further analysis.
Species within Errinopora are unique with the Stylasteridae in having both dimorphic gastro-and dactylopores, a condition first noted by  for three Alaskan species but interpreted exclusively as secondary dactylopores. Careful examination of longitudinal sections of several of these pores reveal that they contain not dactylostyles, but rather small gastrostyles. This implies that most species of Errinopora (all but E. fisheri and E. cestoporina Cairns, 1983, see Table 1) have two types of gastrozooids (feeding polyps), a unique case for stylasterids but previously reported for the hydractiniids Stylactaria conchicola (see Namikawa et al. 1992). Secondary gastropores differ from primary gastropores in being narrower and deeper, and in having only a minute or no gastrostyle. All but one species (E. fisheri, see Table 1) also have dimorphic dactylopores: a large type surrounded by a prominent horseshoe-shaped spine, and smaller, flush pores only 40-110 µm in diameter, which do not have dactylostyles and are termed secondary dactylopores.
In comparison to other stylasterid genera, Errinopora is most similar to Gyropora Boschma, 1960, whose only species, Gyropora africana Boschma, 1960, has dactylopore spines and gastropores coordinated in pore rows, as in some species of Errinopora. Errinopora is also similar to Errina Gray, 1835 andErrinopsis Broch, 1935, whose species may also have thick-walled dactylopore spines. None of these genera, however, include species with dactylostyles, as in Errinopora. Among genera with species having dactylostyles, only species of Errinopora, Inferiolabiata Broch, 1951, andParaerrina Broch, 1942 lack a coordination of gastropores and dactylopores in well-developed cyclosystems (whereas species of Stenohelia Kent, 1870, Stylantheca Fisher, 1931, Stylaster Gray, 1831and Calyptopora Boschma, 1968 do have both dactylostyles and well-developed cyclosystems). Inferiolabiata differs from Errinopora in many characters, in particular by having thin-walled dactylopore spines (instead of thick-walled) that are markedly truncated at the tip (instead of rounded), whereas Paraerrina Broch, 1942 differs in having delicate dactylostyles (instead of robust) and either flush or only slightly raised dactylopore spines-instead of tall and robust (Cairns 1984(Cairns , 1991. Errinopora is also one of the few stylasterid genera with species having calcitic, rather than aragonitic, colonies (Thompson and Chow  Lowenstam 1964, Cairns andMacintrye 1992). The only other stylasterid genera with species known to have mostly calcitic colonies are Errinopsis, Errina, and one species of Stylaster-Stylaster verrillii (Dall, 1884) (see Cairns and Macintrye 1992). Within Errinopora, only E. cestoporina, known solely from the Subantarctic Region, is known to have coralla formed by precipitation of aragonite. This result confirms the more general observation of the prevalence of calcitic stylasterids in the North Pacific (Cairns and Macintrye, 1992), possibly related to the shallower depth of the Aragonite Saturation Horizon (ASH) in the Region (Guinotte et al. 2006).
In an attempt to investigate phylogenetic relationships, 37 partial mitochondrial rDNA 16S sequences were obtained for the six species of Errinopora from the Aleutian Islands, including the holotypes of E. dichotoma, E. disticha, E. fisheri and E. undulata. Based on Lindner et al. (2008), Lepidotheca chauliostylus Cairns, 1991 and Inferiolabiata lowei (Cairns, 1983) were used as the most closely related outgroups. The monophyly of Errinopora is well supported with 100% bootstrap support, but both maximum likelihood and parsimony analyses do not provide strong support for a particular relationship within the genus, resulting in a basal polytomy (results not shown). We thus aligned and analyzed solely the 37 Errinopora sequences but, similarly, no support was obtained for particular phylogenetic relationships within the genus (Fig.  4). Despite low bootstrap support, three of the six most parsimonious trees recover all morphologically-determined E. nanneca  specimens as a monophyletic clade, except specimen USNM1123524, which clusters together with E. undulata. The difficulties in estimating phylogenetic relationships for the Alaskan species of Errinopora using rDNA 16S may stem from relatively recent divergence times. The fossilcalibrated chronogram estimated by Lindner et al. (2008) included E. nanneca (specimen USNM1027820) and E. zarhyncha Fisher, 1938 (specimen USNM1071915), and shows that these species diverged only about 4 million years ago. Moreover, the same study shows that Cyclohelia lamellata Cairns, 1991 andDistichopora borealis Fisher, 1938, two sympatric Alaskan stylasterids that are also clearly distinguishable with marked morphological differences (see above), may have diverged as recently as 1 million years ago. These results indicate that part of stylasterid species diversity in Alaska may have diverged only within the past 1-4 million years and, at least for Errinopora, the results presented herein show that despite the marked morphological differences, some species are not recovered as reciprocally monophyletic lineages (Baum andShaw 1995, Avise 2000)  When arranged in rows, dactylopore spines predominantly in bilateral (distichoporine) rows, the dactylotomes of both rows facing the flanked gastropore row (spines may also be isolated, in pseudocyclosystems, and/or arranged in unilateral rows   and described the genus Errinopora (Fisher, 1931).
Material examined. Holotype. Description. Holotype (Fig. 5A) uniplanar with a secondary flabellum at midheight, 9 cm in height and 6.5 cm in width, with a basal branch diameter of 10 × 7.5 mm. Branches circular to slightly elliptical in cross section and irregularly dichotomous, small-diameter branches often diverging from larger main branches; branch anastomosis absent. Coenosteum reticulate-granular in texture, the strips being 80-90 µm in width and covered with small granules 5-15 µm in diameter; strips bordered by slits 40-45 µm wide. Coenosteum light orange.
Dactylopore spines favor one face of corallum over the other, arranged in abcauline, crescent-shaped terraces flanking one or two gastropores ( Fig. 6A-D). Terraces sometimes almost completely surround a gastropore ( Fig. 6C-D), resembling a cyclosystem of 1.5 mm diameter with an adcauline diastema, much as in Stylaster, but isolated dactylopore spines also fairly common, especially near base of colony. Dactylopore terraces quite thin (0.35 mm) and up to 1.5 mm in height, and, although laterally fused, the individuality of each dactylopore spine is subsumed into the more continuous terrace structure; compound dactylopore spines absent; exterior surface of spines longitudinally ridged. Terraces often horizontally oriented on branches, and slightly flared around gastropore(s). Dactylotomes not slit-shaped as in most other Errinopora, but instead small elliptical pores about 0.27 mm long and 0.15 mm in width occurring only near tips of spine structure; dactylotomes always directed toward a gastropore. Dactylostyles small, about 50 µm in width, having stubby elements up to 25 µm in length and 10-15 µm in diameter. Secondary dactylopores absent.
Gastropores circular, flush with coenosteum, 0.3-0.5 mm in diameter, being fairly consistent in size; gastropores isolated, not arranged in rows; secondary gastropores  absent. Gastropore tube cylindrical, but with a slight medial constriction; often a ring palisade is present, the elements 50 µm tall and 15-25 µm in diameter. Gastrostyle squat, an illustrated one being 0.33 mm tall and 0.29 mm in diameter (Fig. 6I). Gastrostyles covered with longitudinal anastomosing ridges as consistent with the genus. Female ampullae (Fig. 6D) hemispherical but often irregular in shape due to protrud- ing dactylopore spines. Female ampullae 1.0-1.2 mm in diameter; efferent pores not observed. Male ampullae unknown.
Remarks. Even though represented by only one specimen, Errinopora fisheri can be distinguished from other Alaskan congeners by the distinctively terraced arrangement of its dactylopore spines, its small elliptically-shaped dactylotomes, its squat gastrostyles, and its constricted gastropore tube with a ring palisade (see Dichotomous Key and Table 1). Most of these features, however, are shared with E. cestoporina, a species known only from Burdwood Bank and off Tierra del Fuego at 359-384 m. E. cestoporina differs in having differently shaped ampullae, a different corallum color (white), small perforated mounds covering the coenosteum, and a differently shaped gastrostyle.
Distribution. Known only from Aleutian Islands: off Attu Island; 455-458 m. Etymology. The specific name undulata (from the Latin undulatus, meaning wavy) refers to the sinusoidal margin of the lamellate colonies.

Errinopora undulata
Material examined. Types. Description. Colonies lamellate, but wavy in construction resulting in a continuous, thin (1.7-2.0 mm thick), sinusoidal distal edge. Largest colony (USNM 1123528, Fig. 5F) 13 cm tall and 15 cm wide, with a massive basal branch 4.5 × 2.5 cm in diameter; holotype (Fig. 5C) smaller and less intact, measuring 12 cm tall and 11 cm wide, with a basal branch 3.5 × 2.8 cm in diameter. Parasitic spionid worm tubes found in only one colony (USNM 1123528). Coenosteum quite porous, consisting of a reticulum of narrow spiny strips separated by even wider slits, the spines being 10-15 µm in diameter. Coenosteum orange.
Dactylopore spines occur equally on both branch faces, but less abundant toward corallum base. Most dactylopores clustered around isolated gastropores in pseudocyclosystems, 3-5 spines surrounding one pore (Fig. 7B). Pseudocyclosystems most common toward base of colony but also occur frequently on more distal parts of corallum where they are interspersed with short, transverse rows of dactylopore spines that border the distal margins of one or more gastropores, their dactylotomes facing upward (abcauline) toward the gastropore; compound dactylopore spines absent. Dactylopore spines fairly short (rarely taller than 0.25 mm), 0.40-0.45 mm in width, and thin walled, the majority of width being the dactylotome; dactylopore spine walls longitudinally ridged. Dactylostyles robust (  Gastropores circular, flush with coenosteum, and 0.3-0.45 mm in diameter; secondary gastropores about 0.19 mm in diameter. Gastropore tubes short and lack a ring palisade. Gastrostyles lanceolate, the figured style ( Fig. 7G) 0.54 mm in height and 0.29 mm in diameter, covered with longitudinal anastomosing spiny ridges.
Remarks. Errinopora undulata is quite similar to the lamellate form of E. nanneca, but differs in a number of points, one being its colony form, which is a continuous wavy sheet of corallum, whereas that of E. nanneca is more like a series of smaller dissected flat blades of a larger plate. E. undulata also has shorter (0.25 vs 0.4 mm) and thin-walled (vs thick-walled) dactylopore spines, and larger gastropores (0.45 mm vs 0.20 mm in diameter) (see Dichotomous Key and Table 1).Of the 247 known stylasterid species (Appeltans et al. 2011: WoRMS database: www.marinespecies.org) only five have adopted a lamellate corallum shape, four of these occurring in the Aleutian Islands (Cyclohelia lamellata, Stylaster repandus, E. nanneca, and E. undulata), the fourth being the Hawaiian Distichopora anceps Cairns, 1978. Distribution. Known only from the Aleutian Islands: Amukta Pass and south of Semisopochnoi Island; 350-640 m (unconfirmed). Etymology. The specific name disticha (from the Greek distichos, meaning "of two rows") refers to the short distichoporine pore rows of this species.

Errinopora disticha
Material examined. Types. Description. Colonies uniplanar to multiplanar, consisting of cylindrical to highly compressed branches, the greater axis of compressed branches oriented in plane of colony flabellum and reaching up to two times length of lesser axis. Branching dichotomous and non-anastomotic, terminating in blunt tips and forming U-shaped axils be-tween branching. Holotype (Fig. 5D) 10 cm tall and equally wide, with a basal branch diameter of 22 × 20 mm; largest specimen (USNM 1123523) 13.5 cm in height. Parasitic spionid polychaete tubes found in only one corallum (USMM 1123525). Coenosteum typical for the genus: reticulate spinose, the narrow strips separated by broad porous slits, resulting in a very porous surface. Coenosteum light orange; branch cores white or lighter orange.
Dactylopore spines mostly arranged in long meandering distichoporine (bilateral) rows of up to 18 laterally fused spines ( Fig. 8A-B). Two rows or terraces of dac- tylopore spines usually flank each gastropore row, the dactylotomes facing the gastropore; however, the number of dactylopore spines is often unequal on either side of a pore row and are occasionally absent from one side. Toward corallum base, pore rows decrease in length, often resulting in a single gastropore surrounded by 3-6 dactylopore spines approximating a pseudocyclosystem. Dactylopore spines fairly short (0.5-0.9 mm in height) and thick-walled, the dactylotome consisting of onethird to half width of spine; compound dactylopore spines common. Dactylostyles robust, up to 75 µm in width, consisting of cylindrical elements up to 53 µm in length and 5-10 µm in diameter; exterior surface longitudinally ridged. Secondary dactylopores, which lack styles, very common on coenosteum, especially back sides of dactylopore spines, these pores being circular, flush with the surface, and measure about 75-110 µm in diameter.
Gastropores circular, flush with coenosteum, and variable in size, ranging from 0.3-0.7 mm in diameter, both size classes often adjacent to one another. Gastropores usually closely spaced and unilinearly arranged in a shallow sulcus created by adjacent dactylopore spine terraces. Gastropore tubes cylindrical, fairly shallow, and lack a ring palisade; secondary gastropores 0.19-0.30 mm in diameter. Gastrostyles lanceolate but somewhat stout, the figured symmetrical style ( Fig. 8H-I) being 0.49 mm in height and 0.36 mm in diameter, however, many gastrostyles are asymmetrical, being elliptical to flattened in cross section. Gastrostyles bear longitudinal, spiny, anastomosing ridges, and fill most of gastropore cavity.
Female ampullae ( Fig. 8A-B) hemispherical to somewhat flattened (1.3-1.5 mm in diameter), their basal perimeter often slightly undercut, and often with an irregular or ridged surface. Discrete efferent pores never observed. Male ampullae small, porous, hemispherical blisters 0.4-0.6 mm in diameter, often occurring in great concentrations on coenosteum.
Remarks. E. disticha is the only Alaskan Errinopora species to have its dactylopore spines arranged bilaterally in distichoporine rows flanking a row of gastropores, however two other species have a distichoporine arrangement: E. pourtalesii (California) and E. stylifera (Japan to Okhotsk Sea) (see Dichotomous Key and Table 1). E. disticha differs from those two species in having reticulate-spinose coenosteum (vs reticulate-granular), and flattened gastrostyles and branches. Of the 10 specimens examined, 4 are female and 6 male.
Distribution. Known only from the Aleutian Islands: off Petrel Bank, Amukta Pass, and off Four Kings Islands; 178-536 m.  Table S1: 3 (phylogeny and DNA sequences). Errinopora zarhincha: Lowenstam, 1964: 382-383 (misspelling). Description. Colonies uniplanar or multiplanar, robust, with fairly close dichotomous branching, leaving little space between branches; branch anastomosis occurs but uncommon. Largest colony 26 cm in height and 27 cm in width, with a massive basal branch 4.3 cm in diameter (USNM 1123446). Branches circular to slightly flattened in cross section, attenuating to thick (7-15 mm in diameter), blunt tips. Parasitic spionid polychaete worms form tubes along branch axes in two colonies (USNM 96233, 96234), the tubes Fig. 8 in cross section. Coenosteum quite porous in texture ( Fig.  9E-H), consisting of a reticulum of thin (25 µm), spinose ridges, separated by wide slits or series of pores. This texture also present on ampullae and dactylopore spines, in the latter the coenosteal strips forming longitudinal ridges. Coenosteum orange.
Dactylopore spines occur on all branch surfaces and are quite variable in orientation, sometimes forming rows of 10-13 spines laterally fused into a short tier on one side of a pore row (unilaterally), the dactylotomes usually facing upward (abcauline), but dactylopore spines also oriented with their dactylotomes facing downward (adcauline) or laterally, and occasionally are isolated; compound dactylopore spines common. Dactylopore spines quite large and thick-walled, up to 3 mm in height and 1.5 mm in width, the dactylotome occupying one-fourth to one-third width of spine; exterior surface longitudinally ridged. Small, circular, flush secondary dactylopores, measuring only 0.08-0.11 mm in diameter, occur on walls of dactylopore spines, often several on each spine. Whereas dactylopore spines are quite large, dactylostyles are small and thin, only about 30-35 um in width, bearing short spines up to 23 µm in length and 14 µm in diameter.
Gastropores circular and quite variable in size, up to 1.1 mm in diameter, often arranged linearly in valleys created by adjacent rows of dactylopores. Large gastropores often sit directly adjacent to much smaller ones; secondary gastropores about 0.38 mm in diameter. Gastropore fairly shallow, lacking a ring palisade, affording an easy view of base of pore, as the gastrostyle occupies only a small part of gastropore cavity. Gastrostyles lanceolate and slender, up to 0.9 mm in height, and bear longitudinal anastomosing ridges, the gastrostyle size commensurate with diameter of gastropore tube.
Female ampullae inconspicuous (Fig. 9J) and not common, rarely seen in cross section branch fracture. Female ampullae hemispherical, often overshadowed by tall dactylopore spines or becoming incorporated into dactylopore spines. Efferent pores elusive; when detectable they are lateral in position, and about 0.7 mm in diameter, but more often a spent female ampulla lacks its upper half or is simply a crater in the coenosteum, a function of its thin, porous coenosteal cover. Male ampullae equally inconspicuous (Fig. 9C), roughly hemispherical, highly porous, and only about 0.6-0.7 mm in diameter.
Remarks. Errinopora zarhyncha is one of three species in the genus having a predominantly unilateral arrangement of dactylopore spines in which only one row of laterally fused spines (usually the proximal row) have their dactylotomes facing a gastropore or gastropore row, the other species being E. nanneca and E. dichotoma (see Dichotomous Key and Table 1). Errinopora zarhyncha differs from the other two species in having very tall dactylopore spines, relatively small dactylostyles, large robust colonies, and gastropore tubes that are much larger than their gastrostyles (see Dichotomous Key and Table 1). Naumov (1960) reported this species from the Kurile Islands, but based on his description in which he reports gastropore diameters of only 0.20-0.25 mm and dactylopore spines only 0.6 mm in height, we conclude that he is referring to a different, and as yet unknown species. Of the 8 lots of specimens examined, 4 are female, and 4 male. Coralla were determined to be calcitic by Thompson and Chow (1955) and Cairns and Macintrye (1992).
Distribution. Endemic to Aleutian Islands in a somewhat disjunct distribution: Amchitka Pass, Bowers Bank, and off Seguam Island; 207-658 m.  http://species-id.net/wiki/Errinopora_nanneca Figs 5B,G-I, 10A-K Errinopora nanneca Fisher, 1938: 538-539, pl. 66, fig. 1  Description. Colonies quite variable in shape. Most colonies examined uniplanar, consisting of irregularly dichotomous, non-anastomotic branching (e.g., the holotype, Fig. 5B). The opposite extreme is multilobate and multiplanar colonies (Fig. 5H), composed of thin blades of corallum set in a three dimensional arrangement. Virtually all intergrades in colony shape were observed, including some having both large flattened lobes and slender branches (Fig. 5G). Tallest colony examined (USNM 96252) 21 cm in height with a basal branch diameter of 3.5 cm, but a broken colony having a basal diameter of 4 cm (USNM 1123516) implies an even larger size. Although distal branches often circular in cross section, more often they are somewhat compressed in branching plane. Parasitic spionid polychaete worms often form tubes along axis of branches, Fig. 8 in cross section. Coenosteum reticulate-spinose, the narrow strips only about 60 µm wide and bordered by slits of equal width, each strip bearing irregularly unilinearly arranged spines, altogether producing a porous or rough coenosteal texture. Coenosteum light orange to light pink.

Errinopora nanneca
Dactylopore spines isolated or arranged in transverse to oblique rows on distal branches, their dactylotomes facing upward (abcauline), their edges often fusing with edges of adjacent dactylopore spines. On more proximal branches and the basal branch, dactylopore spines fewer in number, and arranged in pseudocyclosystems, short rows, isolated, or as circles around small islands of 2-5 gastropores. Dactylopore spines strongly favor one face of corallum, and are much less common on opposite face. Dactylopore spines relatively small, only about 0.4 mm in maximum height and 0.30-0.35 mm in width, the dactylotome occupying middle third. Small (40-115 µm in diameter) secondary dactylopores flush with coenosteum common. Outer surface of dactylopore spines prominently ridged; inner surface bears a moderately robust dactylostyle (40-50 µm in width, Fig. 10J-K) composed of elements up to 18 µm tall and 7 µm in diameter.
Gastropores circular and flush with coenosteum, 0.15-0.44 mm in diameter, the average about 0.20 mm. Gastropore tube cylindrical, without a ring palisade. Gastrostyles lanceolate, up to 0.55 mm in height, bearing spinose longitudinal, sometimes anastomosing, ridges that themselves bear small spines up to 32 µm long and 8 µm in diameter. Smaller secondary gastropores, lacking gastrostyles, also present, these 0.11-0.19 mm in diameter.
Female ampullae (Fig. 10C) large hemispheres 1.1-1.8 mm in diameter, occurring fairly densely and equally on both corallum faces. Dactylopore spines often occur on female ampullae. Efferent pores rarely observed, but are lateral and up to 0.5 mm in diameter. Male ampullae smaller mounds 0.4-0.7 mm in diameter, clustered, and somewhat irregular in shape. Both types of ampullae porous, like the coenosteum.
Remarks. Errinopora nanneca is one of three species in the genus having a predominantly unilateral arrangement of dactylopore spines in which only one row of laterally fused spines (usually proximal to gastropores) have their dactylotomes facing a gastropore or gastropore row, the other species being E. zarhyncha and E. dichotoma (see Dichotomous Key and Table 1). E. nanneca is distinguished from E. zarhyncha in the account of the latter species, but differs from E. dichotoma in having shorter dactylopore spines and smaller gastropores, uniplanar colonies, and prominently ridged dactylopore spines. Of the 126 specimens examined, 58 are female, 42 male, and 26 indeterminate in gender. The corallum was found to be 100% calcitic according to Cairns and Macintrye (1992).
Distribution. Aleutian Islands from eastern Rat Islands to Islands of Four Mountains, including Petrel Bank; 40-517 m. Etymology. The specific name dichotoma, meaning "in two parts" (from the Greek dicha, meaning "in two" and tomos, meaning "part" or "slice"), referring to the dichotomous branching mode of this species.

Errinopora dichotoma
Material examined. Types. Description. Colonies three dimensional, robust, and sparsely branched, branching equally and widely dichotomously, resulting in broad U-shaped axils; branch anastomosis absent. Largest colony (holotype, Fig. 11D) 11.5 cm in height, with a basal branch diameter of 16 × 20 mm. Branches circular to elliptical in cross section, attenuating to thick (7-8 mm in diameter), blunt tips; tips of most branches missing (broken) from type material. As in most species of Errinopora, coenosteum quite porous (Fig. 12F-I), composed of a reticulum of thin, spinose strips separated by wide slits or series of pores, the spines being up to 55 µm in height and 15-24 µm in diameter. Coenosteum orange, branch cores being white. Dactylopore spines occur on all branch surfaces and quite variable in orientation (Fig. 12B), sometimes forming transverse or longitudinal rows of up to 7 laterally fused spines, spines sharing the same laterally fused row sometimes oriented in opposite directions, their dactylotomes facing in opposite directions. Isolated dactylopore spines also present. Dactylopore spines of moderate size and thick-walled, up to 1.2 mm in height and 1.1 mm in width, the dactylotome occupying one-fourth to one-third width of spine. Small (80 µm diameter), circular secondary dactylopores common. Dactylostyles robust (Fig. 12C, L-M), each about 0.125 mm in width, composed of elements up to 40 µm in height and 10-12 µm in diameter.
Intact female ampullae never observed, but coenosteal depressions 1.0-1.1 mm in diameter are common in one specimen, these presumed to be spent female ampullae. Male ampullae small, porous hemispheres 0.5-0.6 mm in diameter.
Remarks. Errinopora dichotoma is one of three species in the genus having a predominantly unilateral arrangement of dactylopore spines in which only one row of laterally fused spines (usually proximal to gastropores) have their dactylotomes facing a gastropore or gastropore row, the other species being E. nanneca and E. zarhyncha. E. dichotoma is compared to those species in their respective accounts and in the Dichotomous Key and Table 1. Of the five specimens examined, 1 was presumed to be female and 4 male.

Genus Stylaster Gray, 1831
http://species-id.net/wiki/Stylaster Diagnosis. Colonies branching in a flabellum or a bush shape (in only one case lamellate). Coenosteum usually reticulate-granular but may be linear-imbricate; coenosteum of many colors and hardness. Gastro-and dactylopores arranged in conventional cyclosystem arrangement, with only one gastrostyle per cyclosystem; pores of the peripheral type; supernumerary dactylopores often present. Cyclosystems arranged on branch edges and/or on corallum faces, or uniformly on all branch surfaces, but not unifacially. Gastropore tube single-chambered, but may be constricted by a ring palisade. Dactylostyles present. Ampullae usually superficial.
Discussion. The genus and its various grouping are discussed by Cairns (1983b) and a key to all stylasterid genera, including the groups of Stylaster, is provided by Cairns (1992). Currently there are 80 recognized Recent species and 7 fossil species (Appeltans et al. 2011: WoRMS data base: www.marinespecies.org). It is by far the most species-rich and diverse genus of the stylasterids.

Stylaster (Group A)
Diagnosis. Species of Stylaster in which coralla form branching colonies, and in which cyclosystems are uniformly arranged on all sides of cylindrical, blunt branches.

Stylaster brochi
Cyclosystems circular, 0.9-1.1 mm in diameter, and slightly (about 1 mm) raised above coenosteum; cyclosystems uniformly arranged on three or all four sides of a branch, rarely in a linear fashion. Gastropores 0.35-0.40 mm in diameter. Gastropore tubes cylindrical, curved (Fig. 13J), and long (often 2-3 times length of gastrostyle), the length and curvature of tube making it difficult to see gastrostyle tip when viewed from above. Ring palisade absent or diffuse, the elements about 50 µm in height and diameter. Gastrostyles lanceolate and up to 0.7 mm in height, bearing long spines up to 70 µm in length.
Female ampullae (Fig. 13J) superficial hemispheres 0.8-1.1 mm in diameter; efferent pores rarely expressed, but if present, occurring in lateral position and somewhat recessed into coenosteum, each about 0.25 mm in diameter. Male ampullae (Fig. 13K) primarily internal, visible on coenosteal surface only as low mounds 0.3-0.5 mm in diameter, often with a small (30 µm diameter) apical efferent pore. Male ampullae often occur in high density clusters, directly adjacent to one another.
Remarks. Virtually every colony of Stylaster brochi examined contained commensal spionid polychaetes of the genus Polydora (K. Fauchald, per. comm.) , such that this character was informally used to distinguish it from other Stylaster species, such as S. campylecus. Almost every branch is bored axially by this robust worm, which forms binary longitudinal tubes 0.7-0.8 mm in diameter that are figure 8-shaped in cross section (Fig. 15K). Several worms may occur in the same colony, each having one or more efferent openings somewhere on the colony surface. It is easy to conjecture an advantage to the worm in this relationship, i.e. a secure place to live and protection from predators, but it is difficult to imagine an advantage to the stylasterid, as the worm must weaken the strength of the branches as well as compete for the same filtered plankton in the water. Thus, it would seem that these polychaetes are parasites on the coral. Large colonies of S. brochi also form substantial three dimensional habitats for a variety of invertebrates, including sponges, bryozoans, hydroids, barnacles, bivalves, and ophiuroids. Heavy encrustation by sponges seems to promote a more delicate colony growth form, in which the terminal branches are only 1.5 mm in diameter (Fig. 11E). In a monograph otherwise devoted to stylasterids from Sagami Bay, Japan, Eguchi (1968) inexplicably described Allopora abei from "the Aleutian Islands." Although the type was not examined, and Cairns (1983b) suggested a synonymy with Stylaster polyorchis Fisher, 1938, the illustrations provided by Eguchi suggest a synonymy with S. brochi.Of 86 colonies examined, 35 are female, 40 male, and 11 indeterminate, resulting in a fairly equal sex ratio.S. brochi is one of the most common and one of the largest growing stylasterids in the Aleutian Islands. It can be distinguished from other Alaskan species in Stylaster (Group A) by its usually planar growth mode, higher number of dactylopores per cyclosystem, and variable width of its pseudosepta (see Table 2 for additional comparisons).
Distribution. Widespread throughout Aleutian Islands from west of Attu Island to Unalaska (including Petrel Bank), with one disjunct record near Sharma (near Anchorage); 75-351 m, but most records between 100-200 m.
Stylaster stejnegeri   (Fig. 11C) is a small, arborescent colony 6 cm in height and 7 cm in width, with a basal branch diameter of 9.3 mm. Branches cylindrical and blunt tipped, the tips measuring 3-5 mm in diameter. Coenosteum reticulate-granular in texture, coenosteal strips 50-55 µm wide, separated by slits 13-15 µm wide. Coe- Cyclosystems on all sides of branches, circular, 1.0-1.2 mm in diameter. Gastropores circular, 0.35-0.45 mm in diameter. Gastropore tube cylindrical and usually slightly curved such that gastrostyle tip is not visible from apical view; ring palisade absent. Gastrostyle lanceolate.
Female ampullae (Fig. 14A, I-J) superficial hemispheres up to 1.1 mm in diameter, often bearing low ridges radiating from their apex. Male ampullae unknown.
Remarks. Although only one specimen is known of this species, it does appear to be distinctive. Perhaps most similar to S. brochi, it differs from that species in having flush cyclosystems, fewer dactylopores per cyclosystem, and ridged female ampullae (Table 2).
Distribution. Known only from one specimen from the type locality.   Description. Colonies arborescent, dichotomously branching to form a three dimensional bush; branch tips blunt to slightly clavate, 3.0-4.5 mm in diameter. Largest colony (USNM 1027819, Fig. 11B) 3.5 cm tall, 7.0 cm wide, and attached by a basal branch 11 mm in diameter. Colonies usually attached to stones or bivalve shells. Coenosteum reticulate-granular in texture, coenosteal strips 52-55 µm wide, separated by thin slits 10-13 µm wide. Strips covered with small (8-10 µm in diameter) spines, occurring 4-5 across width of a strip, conferring a fine, granular or "sugary" texture. Coenosteal papillae common. Most colonies infested with spionid worms and their characteristic binary tubes (Fig. 15A, K). Coenosteum light orange.
Cyclosystems occur on all sides of branches, circular, and 1.0-1.2 mm in diameter. Gastropore circular and small (0.25-0.30 mm in diameter). Gastropore tubes funnel-shaped near surface but cylindrical adjacent to gastrostyle, straight, and often quite long in thick branches. Ring palisade robust near gastrostyle tip, composed of squat, clavate elements about 40 µm in diameter. Gastrostyles lanceolate to elongate (up to 1.5 mm, Fig. 15H), with a pointed tip; gastrostyles covered with anastomosing, longitudinal, spiny ridges, the spines quite long (up to 65 µm in length) and sharp.

Remarks. Stylaster verrillii is similar to Stylaster venustus
Material examined. Types. Description. Colonies firmly attached to a hard substrate by a robust basal stem and encrusting base, the base being 9 cm in diameter and the basal stem 5 cm in diameter in the case of the holotype. Immediately above basal stem the colony divides into two or three lamellae (Fig. 27C), each lamella (or sheet) of coenosteum increasing its surface area by folding its surfaces into a complex three-dimensional structure similar to that of Cyclohelia. Short (up to 15 mm) cylindrical branches project from plane of colony, but always in response to housing a parasitic spionid worm tube. Holotype (Fig.  27A-B) 23 cm tall and 19 cm in width. Coenosteal lamellae thin at edge, only 2.0-2.5 mm thick, and thus easily damaged during collection; basal lamellae up to 10 mm in thickness. All colonies examined heavily infested with spionid worm tubes. Coenosteum reticulate-granular in texture, the strips being about 30 µm wide, bordered by slits about 9-19 µm thick; granules spinose. Coenosteum covered uniformly with small papillae (Fig. 28B). Coenosteum light orange, but central core a light shade of pink.
Cyclosystems equally common on both faces of lamellae, and even occur on lamellar edges, often arranged in transverse rows of up to 15 cyclosystems that parallel lamellar edge; diameter of cyclosystems 1.0-1.15 mm. Gastropore tube funnel-shaped near branch surface, and straight but constricted, the upper diameter being about 0.34 mm in diameter, the constriction corresponding to a diffuse ring palisade, the blunt elements being up to 60 µm tall and 40 µm in diameter. Gastrostyles lanceolate, pointed, and bear longitudinal, spinose ridges. Illustrated style (Fig. 28D) 0.53 mm in height and 0.26 mm in basal diameter.
Remarks. Among the 80 Recent species in the genus Stylaster (Appeltans et al. 2011: www.marinespecies.org), S. repandus is the only one to have a lamellate growth form. It is very similar in growth form to Cyclohelia lamellata and Errinopora undulata, and is one of five stylasterid species to have lamellate colonies (see Discussion of Errinopora undulata).
Distribution. Known only from three localities in the vicinity of Amukta Island, Aleutian Islands; 375-475 m.

Stylaster (Group B)
Diagnosis. Species of Stylaster in which coralla form branching colonies, and in which cyclosystems are arranged primarily on branch edges, but also on anterior and occasionally posterior sides of branches; branches usually delicate.
Cyclosystems linearly arranged on both edges of branches, as well as on anterior face, and occasionally on posterior face. Those on branch edges often closely spaced, sometimes directly adjacent to one another (Fig. 18C) or even coalescent. Cyclosystems circular, elliptical, or irregular in shape, 1.0-1.3 mm in diameter, slightly flared, and standing slightly exsert from branch; gastropores circular, 0.40-0.45 mm in diameter. Gastropore tubes cylindrical and usually slightly curved (Fig. 18M) on distal branches, such that gastrostyle tip is difficult to see; ring palisade often absent or only poorly developed. Gastrostyles lanceolate, about 0.5 mm in height, and occupying only lower quarter of gastropore tube; H:D about 2.3-2.5. Gastrostyle bears spines up to 0.4 mm in length.
Remarks. Fisher (1938: 505) discussed the similarities of S. campylecus and S. polyorchis, but concluded they were different species based on six minor differences: S. polyorchis had smaller cyclosystems, straighter gastropore tubes, no ridges on the inside of the gastropore tube, often linked cyclosystems, a ring palisade, and wrinkled female ampullae. Based on more detailed SEM observations on many more specimens, these differences are considered to be intraspecific variation, the holotype of S. campylecus itself having some linked cyclosystems and wrinkled female ampullae. The ring palisade is absent in most coralla, but in some specimens is weakly developed. S. campylecus tylotus was also compared to but differentiated from typical S. campylecus by  in having a more delicate corallum, a larger ring palisade, a stouter gastrostyle, larger male ampullae, and more dactylopores per cyclosystem, but closer examinations also shows all these character to be within the range of variation of typical S. campylecus (see Table 2). Likewise, no significant differences could be found between S. moseleyanus and S. campylecus, and thus these four taxa are considered to be the same. Interestingly, types of three of the four taxa were collected at Albatross station 3480, prompting Fisher (1938:514) to remark about "the extraordinary number of species and subspecies dredged at station 3480," considering the possibility that hybridism might be taking place.S. campylecus and S. brochi are the two most commonly collected stylasterids in the Aleutian Islands. S. campylecus can be distinguished from other Alaskan species in Stylaster (Group B) by its slightly flared cyclosystems and the linearity of the coenosteal strips near the cyclosystems ( Table 2). The corallum was found to be 100% aragonitic according to Cairns and Macintrye (1992). Of 94 colonies examined, 44 are female, 39 male, and 11 indeterminate, resulting in a fairly equal sex ratio.
Description. Corallum uniplanar, branching equal and dichotomous; no anastomosis of branches. Largest colony (the holotype, Fig. 17E) 8.5 cm in height and 7.0 cm in width, with a basal branch diameter of 8.4 mm. All branches circular in cross section. Commensal spionid polychaetes absent. Coenosteum reticulate-granular in texture, the coenosteal strips 45-55 µm in width, the slits about 15 µm in width; strips; strips not linear near cyclosystems. Coenosteum white. Cyclosystems occur on branch edges and anterior face, but rarely on posterior face, those on edges not aligned in rows. Cyclosystems circular, 1.0-1.1 mm in diameter, and raised only slightly above branch coenosteum. Gastropores about 0.35 mm in diameter, leading to a slightly curved, funnel-shaped upper tube that narrows to a cylindrical lower part that houses the gastrostyle (Fig. 19G-H); ring palisade absent. Gastrostyles elongate-lanceolate, up to 0.6 mm in length, occupying lower half of gastropore tube, its pointed tip easily seen in an intact cyclosystem; H:D about 3.5.
Remarks.  originally differentiated forma leptostyla from typical Allopora moseleyana (=Stylaster campylecus) based on its more slender gastrostyle and smaller male ampullae. We cannot find a difference in ampulla size between forma leptostyla and typical S. campylecus, but the gastrostyle of leptostyla is longer and more slender than that of S. campylecus, occupying more of the gastropore tube (and thus having a higher H:D ratio) and being more visible from external view. In addition to this difference, forma leptostyla differs from S. campylecus in having equal, non-anastomosing branching; branches circular in cross section; less exsert cyclosystems; non-linearly arranged cyclosystems; fewer dactylopores per cyclosystem; and consistently reticulate coenosteal strips (see Table 2). For these reasons this form is elevated to species rank but is considered to be closely related to S. campylecus.

Stylaster trachystomus
Cyclosystems arranged uniformly on branches, not linearly, but fewer in number on posterior face. Cyclosystems rarely circular in shape, rather elliptical or asymmetrical, the longer axis of the ellipse up to 1.8 mm. Gastropore tubes cylindrical, slightly curved, and quite deep (up to 3 mm); a well-developed ring palisade present near gastrostyle tip, composed of squat elements about 50 µm in height and width. Gastrostyles lanceolate, up to 0.67 mm, having a H:D of about 3.1, and occupying lower quarter of gastropore tube. Because of curvature of the long gastropore tube, the short gastrostyle, and the wide pseudosepta, the gastrostyle tip is rarely seen when viewed from above.
Female ampullae (Fig. 20D, G, K-L) superficial hemispheres 1.0-1.3 mm in diameter, having a knobby or papillose surface; efferent pores not evident in material at hand. Male ampullae (Fig. 20M) also superficial swellings 0.50-0.55 mm in diameter. Both types of ampullae clustered on anterior and posterior branch faces.
Remarks.  described this taxon as a subspecies of S. campylecus, distinguishing it from the nominate subspecies by having spongy pseudosepta (Fig. 20F), decurrent pseudoseptal ridges on the inside of the gastropore tube (Fig. 20C), and spiny coenosteal outgrowths (Fig. 20G-H). S. trachystomus is otherwise similar to typical S. campylecus in gastropore tube and gastrostyle shape and number of dactylopores per cyclosystem, but is also similar to S. brochi in arrangement of cyclosystems and in hosting commensal spionid polychaetes; it also has unique characteristics as mentioned above (see also Table 2). Although few colonies are known of this species, because it does present a unique set of characteristics, it is considered valid and herein elevated to species rank. The corallum was found to be 100% aragonitic according to Cairns and Macintrye (1992).
Female ampullae (Fig. 22I) superficial hemispheres 0.8-1.0 mm in diameter, the lateral efferent pores being 0.15-0.20 mm in diameter. Male ampullae (Fig. 22A, J) partially submerged in coenosteum (internal) on distal branches, entirely internal on larger-diameter branches, the outer diameter being about 0.5 mm, the internal diameter of internal ampullae about 0.42 mm; male ampullae often clustered on branch faces.
Remarks. Although Fisher (1938:508) included this taxon as a subspecies of S. campylecus, considering it to be "the southern shallow-water race of campyleca," there are sufficient differences to warrant raising this subspecies to species rank (Table 2). Distinctive features include its bushy delicate colony, extremely small gastropores surrounded by a thick wall, and relatively low number of dactylopores per cyclosystem. Geographically it occurs only off southeastern Alaska in relatively shallow water, not in the Aleutian Islands. Comparisons to the other subspecies are made in the following account.
Distribution. Bays and inland passages of southeastern Alaska from off Kayak Island to just north of Dixon Entrance (i.e., Prince of Wales Islands and Portland Canal); 23-401 m.
Material examined. Types. Description. Corallum shape and branching similar to that of typical subspecies: bushy or flattened bushy with delicate terminal branches. Holotype 7 cm tall and 7 cm wide, with a basal branch diameter of 10.1 × 8.1 mm; largest corallum (USNM 1096625, Fig. 21B) 8.5 × 8.0 cm, with a massive basal branch diameter of 3 cm. Commensal spionid worm tubes absent. Coenosteum reticulate-granular in texture, the coenosteal strips 50-60 µm wide, bordered by slits about 10 µm wide, the strips originally covered with irregularly-shaped nodules that are subsequently covered with smoother granular coenosteum (Fig. 23E shows the transition). Coenosteum white.
Cyclosystems occur exclusively on edges of distal branches, but also on anterior face of larger-diameter branches. Cyclosystems circular to elliptical in shape, the larger axis ranging from 1.1 to 1.5 mm, the abaxial edge slightly raised above coenosteum; gastropores circular, 0.45-0.50 mm in diameter. Gastropore tubes somewhat inflated in upper half, changing to a narrow cylinder proximally; a welldeveloped ring palisade present as in the typical subspecies, the narrow pointed gastrostyle tip projecting through the ring palisade constriction into upper chamber (Fig. 23G) and thus easily visible from above. Gastrostyles elongate-lanceolate (Fig.  23D), occupying lower half of gastropore tube, and up to 0.67 mm in length, having a H:D ratio of 3.1-3.7.
Female ampullae (Fig. 23I) smooth superficial hemispheres 0.9-1.0 mm in diameter, with lateral efferent pores about 0.23 mm in diameter. Male ampullae (Fig. 23J) superficial swellings up to 0.5 mm in diameter, with small apical efferent pores. Both types of ampullae clustered on anterior and posterior faces.
Remarks. Subspecies columbiensis resembles the typical subspecies in many ways, including colony shape and branching, and ring palisade shape, but also differs in a number of small but consistent characteristics (Table 2). Subspecies columbiensis has larger cyclosystems and gastropores, a slightly higher average number of dactylopores per cyclosystem, a more commodious upper gastropore chamber and deeper dactylotome slits, and a more elongate gastrostyle that is easily seen from above. Dixon Entrance appears to be the border between the two subspecies, the typical subspecies occurring to the north and columbiensis occurring to the south of this body of water. Because of the overall similarity of the two taxa, and their consistent minor differences, including their geographic separation, columbiensis is considered as a subspecies or S. parageus. Of 16 colonies examined, 15 are male and one is female.
Distribution. Entire coast of British Columbia (Canada) from Dixon Entrance to off Cape Flattery, Washington (USA); 246-285 m.

Stylaster alaskanus
Remarks. Originally described as a subspecies of S. gemmascens by , Cairns (1983b) later raised alaskanus to species status. Herein it is synonymized with S. cancellatus, but since it has page priority in , S. alaskanus is considered to be the senior synonym (see synonymy above). The types of S. alaskanus differ from most other specimens assigned to this species in having numerous coenosteal papillae, called "thorny outgrowths" by Fisher (1938: 501), which are often aligned in short ridges. Also, the coenosteum is white and the branches of the type series do not anastomose. However, all these differences are considered to be intraspecific variation, as some other specimens assigned to this species have a white corallum, and small colonies, like the types of S. alaskanus, usually do not have anastomosing branches. Furthermore, rarely some coralla of "cancellatus" have coenosteal papillae, which may be a reaction to an unfavorable environmental habitat. Thus, the type series of S. alaskanus, which was collected at the same station as the type of S. cancellatus, is considered to be a somewhat aberrant specimen of what was more widely known as S. cancellatus. A similarly shaped, sieve-like, reticulate colony is known for Errinopsis reticulum Broch, 1951, however, in that species the reticulum is composed of equally-sized branches, whereas in S. alaskanus the reticulum is composed of thick and thin branches. S. alaskanus is distinguished from all other species in its group by having a corallum shaped as a sieve-like reticulum. It is further distinguished from those Alaskan species of group C by having ridged female ampullae (Table  2). Among the 59 specimens examined, 25 are female, 22 male, and 12 indeterminate, a fairly even sex ratio.  (Fig. 21C) colony bushy, 5.5 cm tall and 4.5 cm wide, attached by a basal branch 6 mm in diameter. Branches do not anastomose and are circular in cross section. Coenosteum reticular-granular in texture, the strips 55-60 µm in width, separated by slits 10-14 µm wide; strips covered with small angular granules. Spionid worm tubes absent. Coenosteum white.
Cyclosystems circular to slightly elliptical, 1.0-1.2 mm in diameter, arranged exclusively on branch edges in an alternating fashion, most projecting perpendicular to branch. Gastropores circular and quite large (0.5-0.6 mm in diameter), occupying up to 55% of cyclosystem diameter (Fig. 25F). Gastropore tube cylindrical, curved, and long, such that gastrostyle tip is rarely seen when viewed from above (Fig. 25A). A delicate ring palisade (Fig. 25C-D) occurs near gastrostyle tip, composed of slender cylindrical elements up to 60 µm long and 25 µm in diameter. Gastrostyle slender (H:D = 4.4), the illustrated style 0.53 mm in height, occupying lower quarter of gastropore tube (Fig. 25A).
Remarks. Despite access to a diverse stylasterid collection from the Aleutian Islands, no unequivocal additional specimens could be identified as S. elassotomus, even the paratype of the species not considered to be conspecific. Its distinctive characteristics of having a highly curved gastropore tube, slender ring palisade elements, and a very large gastropore surrounded by very short dactylotomes and pseudosepta distinguish it from all other Alaskan species (see Table 2).
Distribution. Known only from type locality. Etymology. The specific name crassiseptum (from the Latin crassus, meaning "thick" + septum meaning "wall"), in reference to the wide pseudosepta of the cyclosystems.

Stylaster crassiseptum
Material examined. Types. Description. Colonies primarily uniplanar, having no branch anastomosis. Holotype (Fig. 21D) a branch fragment 12 cm in length and 1 cm in basal branch diameter; largest specimen (USNM 1122527) an intact colony 24 cm in height and 19 cm wide, with a basal branch diameter of 4.5 cm. Distal branches circular in cross section, basal branches somewhat rectangular in cross section, the longer axis perpendicular to colony plane; symbiotic polychaetes absent. Coenosteum reticulate-granular in texture, coenosteal strips 60-70 µm in width, separated by very narrow slits only 3-5 µm wide; coenosteal strips not linearly arranged near cyclosystems. Coenosteal granules very low and smooth, conferring a shiny or porcellaneous texture to branches. Coenosteum dense and uniformly pale orange.
Cyclosystems circular, slightly exsert, and relatively small (0.7-1.0 mm in diameter), occurring exclusively on branch edges (Fig. 26A) in alternating fashion (Fig. 26B), most projecting perpendicular to branch. Cyclosystems well spaced, separated by 1-3 cyclosystem diameters from one another on one side of a branch. Gastropores circular, about 0.5 mm in diameter; gastropore tubes cylindrical and slightly curved, having a well-developed ring palisade (Fig. 26I) composed of numerous large squat elements up to 35 µm in height and 50 µm in diameter. Gastrostyles lanceolate and slender, the figured style being 0.48 mm in height and only 0.15 mm in diameter (Fig. 26I), the tip usually seen when viewed from above. Gastrostyle covered with blunt spines up to 33 µm in length.
Distribution. Aleutian Islands from off Kiska to off Atka Islands, Bowers Bank; 291-531 m.
Genus Stylantheca Fisher, 1931 http://species-id.net/wiki/Stylantheca Diagnosis. Colonies encrusting, forming thin laminae on rocks and shells, rarely forming short stubby branches. Coenosteum reticulate-granular and of many colors; coenosteal papillae quite common. Gastro-and dactylopores arranged in cyclosystems, often with more than one gastrostyle per cyclosystem; pores of the peripheral type; supernumerary dactylopores rare. Gastropore tube single-chambered, but may be constricted by a ring palisade. Dactylostyles usually robust. Ampullae usually internal.
Discussion. As summarized by Cairns (1983b), species attributed to this genus have been placed in the genera Allopora, Stylaster, and as a subgenus of Stylaster. Stylantheca papillosa (Dall, 1884) is indeed very similar to Stylaster (Group A, i.e., Allopora). At present the only characters differentiating Stylantheca from Stylaster (Group A) is its tendency to form encrusting colonies, and its tendency to have more than one gastrostyle per cyclosystem, although there are exceptions to both of those criteria. Deeper water colonies of S. papillosa often have short stubby branches, and the northern range of S. papillosa sometimes has only one gastrostyle per cyclosystem (see Remarks of S. papillosa). It is likely that Stylantheca belongs to the Stylaster genus, perhaps as a fifth group, i.e., "Group E", of species sensu Cairns (1983b) that would include encrusting species with a tendency to Description. The typical form is variable in colony shape, those specimens living in a high energy shallow-water environment usually being encrusting, the layer of coenosteum sometimes less than 1 mm thick (Fig. 27E), the gastrostyle base almost resting on the hard substrate. In deeper water, colonies produce short (up to 17 mm), knobby, clavate, cylindrical branches, which originate from the basal encrustation. Only rarely will these branches bifurcate. Although the types of S. papillosa and S. petrograpta are small, beach-worn fragments (Figs 27D, F), the species produces mats up to 30 cm in diameter. Parasitic spionid polychaetes (Polydora ?alloporis Light, 1970) usually present, forming binary tubes/paired burrows throughout the coenosteum. Coenosteum reticulate-granular in texture, the strips about 50-55 µm in width, separate by slits 12-15 µm wide. Short, porous, conical papillae (nematopores?) common on coenosteum, each about 0.13 mm in diameter and equally tall (Fig. 29B, D, F-G). Coenosteum purple, pink, red, and occasionally white, the tips of the clavate branches usually white.
Cyclosystems uniformly arranged on encrustations and on all sides of branchlets; diameter of cyclosystems 0.9-1.2 mm. Gastropore tube highly constricted, the upper larger portion being infundibuliform to spherical, the lower chamber spherical and almost completely occupied by the gastrostyle(s), the two portions of the chamber constricted near gastrostyle tip. Gastropore tube diameter about 0.3 mm, the tube constriction about half that diameter. Just above the constriction numerous small (up to 45 µm in length) papillae form a wide ring palisade (Fig. 29K) further reducing access to lower chamber. Gastrostyles quite variable and sometimes irregular in shape, including globose (Fig. 29K), lanceolate, or triangular. Regardless, gastrostyles bear quite long (up to 50 µm long and 15 µm in diameter) spines that completely obscure the underlying gastrostyle shaft. Usually there is only one gastrostyle per cyclosystem, but occasionally the upper chambers of two cyclosystems are linked together resulting in two gastrostyles in one cavity, and rarely there appears to be 2 gastrostyles in one normal gastropore chamber. In well-preserved colonies, dactylopores are slightly raised above surface of coenosteum; dactylotomes 0.10-0.12 mm wide. Number of dactylotomes per cyclosystem variable, depending on size of cyclosystem, but ranges from 2-12, with common modes of 4, 5 and 8 (see Remarks). Dactylostyles robust (Fig. 29A, C, H), the cylindrical elements up to 55 µm long and 13-17 µm in diameter, not unlike the gastrostyle elements.
Remarks. Although the holotype of Allopora papillosa is a small, worn colony measuring only 9.4 × 6.6 mm in width and containing only 28 cyclosystems (Fig.  27D), it is not difficult to see the similarity to the two syntypes of Allopora petrograpta   (Fig. 27F), also worn specimens (13 and 16 mm in width, constituting over 100 cyclosystems), even though they were collected from shallow water on opposite sides of the Gulf of Alaska. All of the cyclosystems of the type of Stylantheca papillosa have only one gastrostyle, whereas all but four of the cyclosystems of the syntypes of S. petrograpta have one gastrostyle, the other four having two. The more difficult synonymy is with the more southerly species S. porphyra Fisher, 1931, described from shallow water in Carmel Bay, California. S. porphyra is very similar to the encrusting forms of S. papillosa, differing only in usually having more than one gastrostyle per cyclosystem, sometimes as many as 8. Cairns (1983b) reported an average of 3.3 gastrostyles per cyclosystem (mode = 3) for the holotype. Another typical population of S. porphyra is reported herein from Monterey Bay (USNM 1084662), also having multiple gastrostyles per cyclosystem, but just 50 km to the north (USNM 1084663) are colonies otherwise identical to S. porphyra that have only one gastrostyle per cyclosystem. Fisher (1938:530) was uncertain as to the systematic importance of the number of gastrostyles per cyclosystems, suggesting that this character might have subgeneric or even generic discriminating power. We suggest that it is a matter of intraspecific variation and thus synonymize S. porphyra with S. papillosa, resulting in only one valid species in the genus Stylantheca. The number of dactylopores per cyclosystem of S. porphyra ranges from 6 to16 (n = 34, average = 9.11, σ = 2.08, mode = 10) (Cairns, 1983b), whereas it is lower for the type of S. petrograpta (n = 30, range =2-7, average = 5.07, σ = 0.94 , mode = 5) and slightly lower still for the types of S. papillosa (n = 14, range = 3-5, average and mode= 4.0, σ = 0.68). Another typical specimen (AB76-55) having only 1 gastrostyle per cyclosystem has a range of 5-12 dactylopores per cyclosystem (n = 30, average = 7.43, σ = 1.61, mode = 8). The higher number of dactylopores per cyclosystem of S. porphyra is explained by its larger cyclosystems that house multiple gastrostyles, but in general the number of dactylopores per cyclosystem cannot be used as a diagnostic character for this species. Southern populations that have a slightly larger cyclosystems and more than one gastrostyle per cyclosystem can be referred to as the "porphyra" form, a conclusion first suggested by Cairns (1983b: 483). The type of S. porphyra is illustrated by Cairns (1983b) and as Fig. 27G herein. Two other eastern Pacific species are similar to Stylantheca papillosa in color and cyclosystem and gastrostyle shape: Stylaster venustus (Verrill, 1870) and Stylaster californicus (Verrill, 1866). S. venustus (Figs 16A-I, 17F-G) is known from Monterey Bay, California (USA) to Vancouver Island, BC (Canada) at depths of 10-108 m and, although it may originate with an encrusting base (Fig. 17F, MCZ 5525, holotype), it quickly forms small colonies with delicate branches (Fig. 17G). Sixteen locality records are present at the NMNH, most from off Washington and Oregon (USA), but this species is not treated in this review except to illustrate some of its characters (Table 2). On the other hand, the more southern S. californicus, known from off southern California (USA) from approximately 21-45 m (see Boschma 1957), forms large colonies with robust branches; this species is not further discussed in this review except for the table of comparisons (Table 2).
Distribution. Widespread from the Alaska Peninsula (Shumagin Islands) to Monterey Bay, California, although not yet reported from the northern Gulf of Alaska. Common in the inner passages of Alaska and British Columbia; intertidal to 27 m. Forma porphyra known only from Monterey Bay area.

Genus Crypthelia Milne Edwards & Haime, 1849
http://species-id.net/wiki/Crypthelia Diagnosis. Colonies usually uniplanar and quite delicate. Coenosteum linear-imbricate and white; nematopores common. Gastro-and dactylopores arranged in cyclosystems that are arranged unifacially on colony, only rarely on both faces; cyclosystems covered all or in part by a fixed lid. Gastropore tube double-chambered, lacking gastroand dactylostyles. Ampullae usually superficial with a variety of locations of efferent pores.
Discussion. Crypthelia is the second-most species-rich genus in the family, currently boasting 31 Recent and one fossil species (Appeltans et al. 2011: www.marinespecies.org). They are easily recognized by the prominent fixed lid that covers each cyclosystem. They are more characteristic of deep water environment and hold the record for the deepest stylasterid species.