Four new Caribbean Sigambra species (Annelida, Pilargidae), and clarifications of three other Sigambra species

Abstract Sigambra grubii Müller, 1858 has been reported from many different coastal environments in Brazil and the Grand Caribbean. However, more than one species was thought to be included under this species group name. After the study of several subtle and consistent differences in specimens fitting the description S. grubii, a new Grand Caribbean species is herein recognized and described as S. hernandezisp. nov. Further, the study of other Sigambra specimens prompted the examination of type specimens of S. bassi (Hartman, 1947), and of S. wassi Pettibone, 1966 to clarify some morphological features, and three other new species are recognized and newly described: S. diazisp. nov. and S. ligneroisp. nov. from the southeastern Caribbean (Venezuela), and S. olivaisp. nov. from the northwestern Caribbean (México). Morphological features are also clarified for S. grubii by comparison with specimens from the type locality, Florianópolis, Brazil, and with type specimens of S. bassi from Florida (U.S.A.), and non-type specimens of S. wassi from Virginia (USA). A key to identify all species of Sigambra is also included.


Introduction
Fritz Müller (1822Müller ( -1897 was regarded by Darwin as the 'Prince of Observers' after his careful studies of many different plant and animal groups in Santa Catharina, Brazil (Hartfelder 2019). Müller's research interests resulted in 263 published articles, which are certainly remarkable even after current standards. Müller wrote two papers dealing with polychaetes (Hartman 1951): one was part of his series of arguments and examples supporting Darwin, where he referred to an amphinomid living on goose barnacles; the other one was a report about the polychaetes found from Santa Catharina Island, Florianópolis, Brazil (Müller 1858). A panoramic description of the main benthic and pelagic organisms was part of a letter dated November 1856 and sent to his brother Hermann (Möller 1921: 9). Müller (1858) proposed eight new genera and described nine new species from Santa Catharina Island. Six of his genusgroup names are listed as valid in WoRMS: Cherusca, Glycinde, Hermundura, Isolda, Magelona, and Sigambra. Sigambra grubii, the type species for the genus, was briefly described based on a living specimen in 13 text lines and three figures of the anterior end, parapodium, and dorsal hook. Hartman (1947: 483) hesitated about recognizing Sigambra; she thought it could be the same as Ancistrosyllis McIntosh, 1879, and indicated that its status should be solved by the study of topotypes (non-type specimens from the type locality). She later regarded Sigambra as questionably the same as Ancistrosyllis (Hartman 1959: 195). Pettibone (1966: 156, 157, 179 ff) reinstated Sigambra and since then, it has been recorded in many localities along Brazilian coasts. Currently, S. grubii is regarded among the most abundant marine benthic polychaete species along south and southeastern Brazil, in sediments of up to 150 m depth (Rohr and Almeida 2006). However, it has been recorded in over 110 studies along Brazilian coasts (Amaral et al. 2013) from estuarine areas to marine deep-water sediments (1000-3000 m), including the northern Amazonian mangrove region (Cutrim et al. 2018). Given such a wide bathymetric range, more than one species might be included under the same name. Further, because of the lack of a clarification of the morphology of S. grubii, some other unlikely species records have been reported in literature from the region. For example, de Almeida et al. (2012) recorded S. pettiboneae Hartmann-Schröder, 1979, a species originally described from Australia, from Santa Catharina State, Brazil.
The present study was prompted by the finding of Sigambra specimens in brackish waters of Tamiahua Lagoon in the Mexican coastal states of Veracruz and Quintana Roo, and the need to clarify the details of some widely distributed Sigambra species including the amphiamerican S. bassi (Hartman, 1947). Type material of S. bassi, S. wassi Pettibone, 1966, and topotype specimens of S. grubii were studied and compared to specimens from the Grand Caribbean and southern Brazil. We found some subtle and consistent differences in the Grand Caribbean specimens, and they are herein described as new. We also provide additional observations for the topotypes to clarify their differences. A key to identify all species in the genus is also included.

Materials and methods
Tamiahua Lagoon is on the Mexican Gulf of México coast, in the northern part of Veracruz. After a heavy rain season in 1999 a mass benthic mortality or defaunation occurred, prompting a study on the recovery of polychaete benthic communities. Six systematic samplings were carried out at the site, through a network of four transects each with four stations, during November 1999, March, August, and November 2000, July 2001, and February of 2002(Sánchez-Hernández 2009. Sediments were taken with an Eckman dredge and washed through a 0.5 mm mesh screen; polychaetes were fixed in a 10% formalin solution and preserved in 70% ethanol. Material from the southern Brazilian coast was collected from a non-vegetated tidal flat adjacent to salt marshes and mangroves in Pontal da Daniela (27°27'11"S, 48°31'47"W), Santa Catharina Island, Florianópolis. Sediment samples were taken during low tide with a manual PVC corer (10 cm diameter x 15 cm depth), in summer and winter of 2018. Sediments were washed through a 0.5 mm mesh. Specimens were removed and then fixed in a 6% formalin solution in sea water, with Rose Bengal. Specimens were later sorted and transferred to 70% ethanol.
Specimens were often twisted and measuring their length or counting their chaetigers became problematic. For the length, the specimen was carefully set along a ruler and the width measured at approximately chaetiger 10 including dorsal cirri. For twisted specimens, the number of chaetigers is given as an estimate (ca.) when they exceeded approximately 90. Start of dorsal hooks was determined from specimens mounted in a 1:1 solution of glycerin and 70% ethanol and scanned with a compound microscope. For indicating the relative size of median to lateral antennae, specimens were observed in profile, because tips of the median antenna were often damaged. If possible, these appendages were measured directly with a mini scale such as BioQuip 4828M. The first presence of dorsal hooks depended on the visibility of the hook, or at least on their broken handles, when the specimens were viewed along their dorsal parapodial surfaces.
Specimens were often temporally stained with Methyl Green or Shirlastain-A; the latter was especially useful for detecting papillae in the basal pharyngeal ring. Digital photographs were made in both stereo-and compound microscope, and for some species, SEM micrographs were made in the El Colegio de la Frontera Sur (ECOSUR) facility. Photo series were compressed by using HeliconFocus software. The sequence of species described in Systematics is alphabetical. segment and presence of modifications along its anterior margin, the presence of ventral cirri on chaetiger 2, and of a constriction on anterior chaetigers. Parapodial features include the relative size of dorsal and ventral cirri, the start of dorsal hooks and their presence along body, and the type of neurochaetae. For the pharynx, the number of marginal papillae is especially useful. There are two patterns regarding the start of dorsal hooks. In the first, their start tends to be more or less stable, with a very small variation (2-4 chaetigers) disregarding variations in total size or number of chaetigers.
In the other pattern, notohooks start at an earlier chaetiger in smaller specimens, and they are apparently displaced posteriorly during ontogeny, such that larger specimens will have dorsal hooks from a more posterior chaetiger. Further, notohooks along a few anterior chaetigers are often embedded in the notopodial bases, such that it is necessary to observe the specimen under a compound microscope to precise on which chaetiger notohooks arise. This implies that a series of specimens of different size, collected from the same date, and from similar depths, and sediment types, should be analyzed before deciding which alternative to follow in the key below. If available, size ranges were included in parenthesis to help guide decisions in the key, following Nishi et al. (2007). There are four other potentially useful characters. First, the prostomial dorsal surface between the palps (interpalpal region) can be characterized by its anterior margin as blunt or depressed, and by the lateral depressions being widened posteriorly, or rectangular if the lateral depressions are more or less parallel. Second, in some species there is a deep antennal furrow for each lateral antenna; they can be easily noted if distinct, or as indistinct if they are difficult to see; further, antennal furrows are often narrower medially, and then they can diverge slightly, being almost parallel, or markedly divergent. Third, in some species, the ventral cirri can be short, not reaching neuropodial lobes tips, whereas in other species, ventral cirri can reach and even surpass neurochaetal lobes in medial or posterior parapodia. Fourth, the number of posterior chaetigers without hooks: in posterior chaetigers the dorsal hooks tend to be more exposed and are usually larger than those present in medial chaetigers or larger than parapodial lobes. Fig. 1 Ancistrosyllis bassi Hartman, 1945: 6 (contents), 9 (substrate), 15 (non-diagnostic characters), nomen nudum. Ancistrosyllis bassi Hartman, 1947: 501-504, pl. 61, figs 1-7;Hartman 1951: 36-38, pl. 11  Clarification. The holotype ( Fig. 1A) was found in the Gulf of México side of Florida, whereas the paratype ( Fig. 1B) was found in North Carolina. Both specimens are colorless, without any trace of pigmented glands. An additional specimen ( Fig. 1C) was included in the same species, but it was collected in Los Angeles Harbor, and it has some brownish glands in both dorsal tentaculophores and dorsal cirri of chaetiger 1. There are some other differences between these specimens. For example, in the holotype the interpalpal area is slightly projected anteriorly and its margins are slightly divergent posteriorly, the lateral antennae are three times longer than wide, and the lateral antennal depressions are markedly divergent and expanded, such that the anterior region is wider than posterior one. In the paratype the interpalpal area is tapered, reduced anteriorly, with its margins expanded posteriorly, the lateral antennae are 4 times longer than wide, and the lateral antennal depressions diverge laterally such that the anterior region is shorter than the posterior one. The non-type specimen has a truncate interpalpal region, with its anterior margin slightly bilobed, and margins more or less parallel, the lateral antenna are more than 12 times longer than wide, and the lateral antennal depressions are barely distinct, visible only along the inner side of each antenna.

Sigambra bassi (Hartman, 1947)
Remarks. If these specimens are conspecific, the species would have a Gulf of México-Atlantic and Eastern Pacific distribution, which is untenable, for the following reasons. A strong genetic discontinuity between Gulf and Atlantic populations has been noted for specimens living in Florida (Soltis et al. 2006, Bijak et al. 2018, and amphi-American species have been progressively recognized as including more than one distinct species upon morphological features and genetic markers combined (Carrera-Parra and Salazar-Vallejo 2011), or even after the analysis of morphological differences (Conde-Vela and Salazar-Vallejo 2015). Consequently, S. bassi should be regarded as a northwestern Atlantic species restricted to the Gulf of México; new names and descriptions will be provided for the specimens from Beaufort, NC, and Los Angeles, California in a subsequent publication. Chances are, however, that the same species might extend from the Gulf of México to Beaufort, NC On the other hand, it should be noted that specimens from San Francisco have been regarded as belonging to a different species since 2013 (Norris 2013 Diagnosis. Sigambra with median antenna reaching chaetiger 5-7, twice as long as laterals; tentacular segment four times wider than long, anterior margin smooth; dorsal cirri larger than ventral ones; chaetiger 2 without ventral cirri; notopodia with dorsal hooks and capillaries from chaetiger 4-5; median and posterior chaetigers with ventral cirri reaching neuropodial lobes tips; pharynx with 13-16 marginal papillae. Description. Holotype (ECOSUR 214) an anterior fragment, 7.5 mm long, 1.5 mm wide, 41 chaetigers, right parapodia of chaetigers 16 and 40 removed for observing parapodial features. Body obconic, cylindrical along chaetigers 1-22, depressed thereafter. Dorsal integument rugose, weakly areolate, especially along chaetigers 4-16 ( Fig. 2A).
Prostomium blunt, three times wider than long. Palps with palpophores massive, directed ventrally, palpostyles digitate, with a basal oblique mark; interpalpal area distinct, right longitudinal depression better defined than left one, expanded posteriorly. Antennae tapered, median antenna twice as long as laterals, laterals barely surpassing palp tips, median antenna reaching chaetiger 2-3. Lateral antennal depressions distinct, more or less parallel to anterior margin of tentacular segment. Pharynx barely exposed (Fig. 2B). Basal ring not exposed. Distal margin with 14 papillae, four centrolateral ones twice larger than others, each papilla prismatic, tips globular, variably developed. Tentacular segment three times wider than long; dorsal tentacular cirri slightly longer than ventral ones, approximately half as long as dorsal cirri of chaetiger 1.
Notochaetae include dorsal hooks from chaetiger 4, heads of hooks fully exposed initially, progressively larger and exposing handles; one accessory capillary present from chaetiger 13. Neurochaetae include three or four short wide pectinates, approximately ten large thin pectinates, and many long finely denticulate capillaries.
Posterior region missing. In paratype tapered to a blunt cone (Fig. 2E). Pygidium laterally expanded, anus terminal, anal cirri ventrolateral, as long as last five or six chaetigers.
Oocytes not seen in parapodial spaces. Etymology. This species is named after Oscar Díaz-Díaz, Venezuelan polychaete specialist, working now in Chile, as a modest homage to his many publications on polychaetes, and especially because he sampled and processed the specimens including this newly described species. The specific epithet is a noun in the genitive case (ICZN 1999, Art. 31.1.2).
Variations. The paratype was complete. It is 9.5 mm long with 70 chaetigers, but last three chaetigers are hookless. The median antenna is twice as long as the laterals, and the tentacular cirri reach chaetiger 2 or 3 as in the holotype. In the paratype the dorsal hooks start on chaetiger 4, as in the holotype, but although in the holotype the additional capillary is seen from chaetiger 13, in the paratype they are visible from chaetiger 24.
Remarks. Sigambra diazi sp. nov. resembles S. tentaculata  and it has been identified as such in previous studies, but the redescription by Moreira and Parapar (2002) of S. tentaculata helps for clarifying their differences. They differ in the relative shape of dorsal cirri, and in the size of ventral cirri in comparison to neurochaetal lobe. In S. diazi dorsal cirri are tapered, without basal enlargement, and ventral cirri in median and posterior chaetigers are as long as neurochaetal lobes, whereas in S. tentaculata, dorsal cirri are basally widened, and ventral cirri are shorter than neurochaetal lobes along body.
Distribution. Only known from the southern Caribbean coast of Venezuela, in shallow muddy bottoms.
Tentacular segment 4-5 times wider than long, with a single transverse row of globular tubercles, with two or three additional short middorsal series; dorsal tentacular cirri slightly longer than ventral ones, as long (Fig. 4A) or half as long (Fig. 3A, B) as dorsal cirri of chaetiger 1.
Remarks. As indicated in the key below, Sigambra grubii Müller, 1858 resembles S. hernandezi sp. nov. by having dorsal hooks without accessory capillaries. Their main differences are in the size of median antenna, and in the number of posterior chaetigers without hooks. In S. grubii the median antenna is mediumsized, reaching chaetiger 3 or 4, and there are 4-6 posterior chaetigers without hooks, whereas in S. hernandezi the median antenna is shorter, reaching chaetiger 2 or 3, and there are only two posterior hookless chaetigers. Another subtle difference is the relative size of papillae along body: which are larger in S. grubii compared to S. hernandezi.
Distribution. The species was described from Florianópolis, southern Brazil, and although it has been reported from a wide bathymetric range along the Brazilian coast, further investigations of this material might show the species to be restricted to shallow water sediments. An interesting fact about Ilha do Desterro (type locality), former name for Florianópolis is the origin of the name. Florianópolis was meant to be a tribute to Marshal Floriano Peixoto, the second President (1891-1894) of the Republic of the United States of Brazil, by combining the first name with the Greek term polis, meaning city. Up to 1893, the city was called Nossa Senhora do Desterro (Our Lady of Banishment) or simply Desterro.  Diagnosis. Sigambra with median antenna reaching chaetiger 2-3, twice as long as laterals; tentacular segment 4 times wider than long, anterior margin smooth; dorsal cirri larger than ventral ones; chaetiger 2 without ventral cirri; notopodia with dorsal hooks from chaetiger 4-5, without capillaries; posterior region with two hookless chaetigers; pharynx with 13-16 marginal papillae.
Some smaller features are worth mentioning after their observation with SEM. In anterior chaetigers (Fig. 7A) there are some small round papillae or tubercles in the upper, posterior surface of parapodia (Fig. 7B, C), but their tips have 2-5 long cilia, and they probably are sensory structures. The hypertrophied gonopore has a cover of globular smooth, external protuberances (Fig. 7B, D).
Oocytes inside parapodial spaces (Fig. 5D, inset), ca. 100 µm in diameter. Variation. Specimens were 1.7-13.0 mm long, 0.2-2.0 mm wide, 25-104 chaetigers, with dorsal hooks starting on chaetiger 10-28 with a posterior displacement in larger specimens. The specimens from Tamiahua were slightly larger than those in Chetumal (up to 13 mm long, 104 chaetigers) but because the dorsal hooks start from chaetiger 24-26 whereas they start from chaetiger 14 in the smallest specimen (6.5 mm long), they are regarded as belonging to the same species as the one from Chetumal (up to 11.3 mm long, 76 chaetigers, dorsal hooks from chaetiger 26-28; specimens 6-7 mm long had dorsal hooks on chaetiger [19][20][21][22][23][24][25][26]. There were no accessory capillaries with notohooks. The supracicular, wider pectinates ( Fig. 7E-G) have small lateral, paired denticles, when compared to those present in S. grubii. Oocytes and sperm are present along coelom, but in the posterior region, there are mostly spermatids ( Fig. 7H-J), each ca. 1.3 µm in diameter.   . Sigambra hernandezi sp. nov. A larger specimen, Chetumal, dorsal view (asterisk indicates left chaetigers 8-9) B same, chaetigers 8-9, left parapodia, partial dorsal view (asterisk indicates cilia, arrow points to gonopore) C chaetiger 9, left parapodium, axillary ciliated papillae, seen from above D same, gonopore papillae, seen from above E large specimen, Tamiahua, anterior region, dorsal view, asterisk indicates left parapodia of chaetigers 3-4 F same, close-up of chaetae, seen from above G same, rotated, details of denticles in pectinate chaeta H another specimen, posterior region, dorsal view (arrow points to broken posterior chaetiger I same, rotated about 90 degrees, showing inner contents J same, spermatozoa. Scale bars inserted in micrographs. Etymology. This species is named after Dr. Héctor A. Hernández-Arana, quantitative benthic ecologist in ECOSUR-Chetumal, in recognition of his many studies on brackish water environments in southeastern México, and especially because he led the research study where Chetumal Bay specimens were collected. The specific epithet is a noun in the genitive case (ICZN 1999, Art. 31.1.2).
Remarks. Sigambra hernandezi sp. nov. resembles S. grubii Müller, 1858 because they have dorsal hooks without capillaries. They differ especially in the relative size of median antenna, and in the number of posterior chaetigers without hooks. In S. hernandezi the median antenna is short, reaching chaetiger 2-3, and there are two hookless chaetigers in the end of body, whereas in S. grubii the median antenna is medium sized, reaching chaetiger 3-4, and there are six hookless posterior chaetigers. Another subtle difference is the relative size of papillae along body, which are smaller in S. hernandezi and larger in S. grubii.
In Tamiahua Lagoon, S. hernandezi was an important member of the colonizing benthic polychaetes, being rare after defaunation and progressively becoming one of the more abundant species (Sánchez-Hernández 2009), along a wide range of salinity (5-30‰). In Chetumal Bay, S. hernandezi was not among the most abundant species (Hoil-Baeza 2009), and it was common in brackish water seagrasses (Halodule sp.). The specimens included in this study were collected along the western shore of Chetumal Bay, which has the lowest salinity values (Carrillo et al. 2009). The specimens from Venezuela are included here with hesitation because they are in suboptimal conditions, but they have a similar pattern in parapodial development and start of the dorsal hooks.
Notochaetae include dorsal hooks from chaetiger 27, barely exposed, without accessory capillaries. Neurochaetae of two types: smaller and medium-sized fine denticulates and long smooth capillaries. No pectinate chaetae present.
Posterior region features unknown. Oocytes not seen. Variation. A larger specimen was recorded by Liñero-Arana and Díaz-Díaz (2005), and they also provided several illustrations, probably combining some features of both specimens. Their largest specimen was also an anterior fragment but twice as large and with more chaetigers (33 mm long, 5 mm wide, ca. 90 chaetigers). All body features match and they also included an illustration of the far posterior chaetigers; parapodial cirri are tapered, about twice as long as wide, dorsal hooks become more exposed and there is an additional chaeta, thick, slightly falcate, which might correspond to an acicula, instead of a capillary.
Etymology. The species name is after Dr. Ildefonso (Mikel) Liñero-Arana, polychaete specialist from the Universidad de Oriente, Instituto Oceanográfico de Venezuela, Cumaná, in recognition of his many publications about Venezuelan polychaetes. The specific epithet is a noun in the genitive case (ICZN 1999, Art. 31.1.2).
Remarks. Sigambra ligneroi sp. nov. resembles S. wassi Pettibone, 1966 in having similar body, parapodia and prostomial shapes, such that the holotype plus another specimen were identified as the latter species. They differ, however, in several features, the most important ones being the relative size of antennae, the length of parapodial cirri on chaetiger 1, and the number of marginal pharyngeal papillae, or at least their shape. In S. ligneroi the median antenna is twice as long as laterals, dorsal cirri are three times longer than ventral one on chaetiger 1, and there are eight regular papillae on the pharynx. By comparison, in S. wassi antennae are subequal, dorsal cirri are twice as long as the ventral ones (cf. Wolf 1984: 29.7, fig. 29.4c), and there are ca. eight irregularly-defined papillae on the pharynx.
As indicated in the key below, S. ligneroi also resembles S. healyae Gagaev, 2008 because both have ventral cirri on chaetiger 2, and their pharynx has 8 papillae. They differ by the relative size of antennae, and in the start of dorsal hooks; in S. ligneroi median antenna is twice as long as laterals, and dorsal hooks start on chaetiger 26-28, whereas in S. healyae antennae are subequal and dorsal hooks start on chaetiger 4.
Distribution. Only known from the type locality, off Barcelona, Venezuela, in sediments of water depths of 22 m. Diagnosis. Sigambra with median antenna twice as long as laterals; chaetiger 2 without ventral cirri; dorsal cirri larger than ventral ones; dorsal hooks from chaetiger 30-39, without capillaries; posterior chaetigers without capillary notochaetae; pharynx with 13-16 marginal papillae.
Prostomium blunt, four times wider than long. Palps with palpophores massive, as long as wide, palpostyles blunt, short, with an oblique basal mark; interpalpal area dis- tinct, blunt anteriorly, expanded posteriorly. Antennae tapered, median antenna twice as long as laterals (left lateral antenna broken), laterals surpassing tips of palps, median antenna reaching chaetiger 2 or 3. Lateral antennal depressions indistinct.
Tentacular segment eight or nine times wider than long; dorsal tentacular cirri slightly longer than ventral ones (Figs 9B, 10B, C), about half as long as dorsal cirri of chaetiger 1.
Variation. Complete specimens 15-24 mm long, 128-150 chaetigers. Antennae are easily eroded during sieving, but in undamaged specimens the median one is twice as long as lateral ones. Dorsal hooks start in chaetigers 30-39, apparently a size-dependent variation. There are no capillary chaetae with dorsal hooks in posterior chaetigers; last two have no hooks.
Etymology. This species is named after José Juan Oliva-Rivera, amphipod taxonomist in ECOSUR, in recognition of his efforts sampling and processing benthic invertebrates from Nichupté Lagoon, Cancún, México. The specific epithet is a noun in the genitive case (ICZN 1999, Art. 31.1.2).
Remarks. Sigambra olivai sp. nov. resembles S. constricta (Southern, 1921) by having median antenna twice as long as the laterals, and dorsal hooks from chaetigers 30-40. They especially differ in the presence of a constriction on chaetiger 4, and of capillary notochaetae in posterior chaetigers. In S. olivai there is no constriction on chaetiger 4, and there are no capillaries in posterior chaetigers, whereas in S. constricta the body has a constriction on chaetiger 4, and there is a single capillary notochaetae in posterior chaetigers.
Distribution. Only known from Nichupté Lagoon, Cancún, México, in seagrasses, mostly Halodule sp., in sediments of about 1 m depth. Pettibone, 1966 Fig. 11 Sigambra wassi Pettibone, 1966: 186-190, figs 17,18;Wolf 1984: 29-8, fig. 29-4a-j. Clarification. The original illustrations and descriptions deserve some clarifications. Antennae are certainly of about the same length, but they are not tapered but digitate, and surpass the tips of palps, at least the right one (Fig. 11A). The pharynx is Figure 11. Sigambra wassi Pettibone, 1966 A holotype (USNM 30988), anterior region, dorsal view B same, right lateral view C same, frontal view D paratype (USNM 30987), posterior region, dorsal view E same, posterior end. Scale bars: 0.6 mm (A, C), 0.9 mm (B), 0.5 mm (D), 0.2 mm (E). fully exposed, and the basal ring has about 20 irregular hemispherical lobes, but the anterior margin is eroded and damaged (Fig. 11B), such that its marginal papillae are difficult to detect; there are vague indications of the presence of approx. eight large papillae (Fig. 11C). They would include some round projections which might represent the eroded base of papillae, or that they were collapsed when the specimen was compressed into the container.

Sigambra wassi
The posterior end is twisted in the paratype. It had to be pressed by a glass slide in order to have a better observation of the pygidium and anal cirri (Fig. 11D). Anal cirri are delicate, three times longer than pygidial width and tapered (Fig. 11E), not subcylindrical as originally illustrated.
Remarks. After the study of type material, the number of marginal papillae is not defined for S. wassi Pettibone, 1966. Their number might be the same as in S. ligneroi sp. nov. described above, but better specimens are needed to clarify this. On the other hand, most diagnostic features for the species were confirmed by Wolf (1984), the fragility of anal cirri might explain why they were not observed by him. * The key includes two undescribed species being recorded with other names, or not completely identified, but in both cases, they are distinct and deserve to be described. and to the warm hospitality of the late Kristian Fauchald and Len Hirsch, and by our friends Leslie Harris and David Ocker, and Kirk Fitzhugh. Leslie Harris (LACM) kindly shared some observations made by her and other Californian colleagues. Luis F. Carrera-Parra helped us by making some SEM micrographs and catalogued the ECOSUR types. Naoto Jimi kindly shared some publications by Minoru Imajima in Japanese. Chris Glasby and an anonymous referee helped us improve the clarity of this contribution.