Four individuals captured during summer, autumn and winter between 2010 and 2012 (11/10/2010; 03/08/2011; 27/01/2011; 09/01/2012). Voucher: one specimen sectioned sagittally, stained with azan and deposited in the Invertebrate Collections of the MNCN; Cat. Nr: MNCN 4.01/573 to 4.01/599 (27 slides). Further material: one specimen cat. Nr. MNCN 4.01/600 to 4.01/625 (26 slides).

Elongated worms 11 mm long and 6 mm wide. Body shape elongated with light undulating margins and rounded anterior and posterior ends. Dorsal surface with numerous papillae. Colouration orange, yellowish orange or translucent grey with white patches at the mid-dorsal line (Figure 1A, B, C, D). Ventral side smooth and pale. Short inconspicuous marginal tentacles. Sucker located approximately in the middle of the body (Figure 1E). Tentacular eyes scattered over dorsal margin of tentacles (Figure 1A), cerebral eyes in two elongated, anteriorly anastomosing clusters. Plicate cylindrical or tubular pharynx near anterior end, frontally oriented; oral pore posterior to brain. Male and female genital pores clearly separated and posterior to pharynx (Figure 1E).

Male copulatory apparatus located posterior to male pore and oriented mainly dorso -ventrally, but also directed frontally (Figure 1E, F). Male system consists of a short, armed (stylet) penis papilla, a true prostatic vesicle with a smooth glandular epithelium, and a well developed, muscularized seminal vesicle. Prostatic vesicle opens directly into penis papilla, and seminal vesicle empties directly into distal end of prostatic vesicle. Vasa deferentia, sometimes very dilated, open proximally through a common duct (common vas deferens) into seminal vesicle.

Inconspicuous female system lies posterior to the male pore and is characterized by a short female atrium, female duct (vagina), and characteristic uterine vesicles. Abundant cement glands are located around female pore and distal part of vagina.

Cycloporus papillosus is a natural predator of Botrylloides violaceus Oka, 1927 (Ascidiacea), which is a clear example of an invasive species. Botrylloides violaceus grows on all types of substrates, including other living animals such as mussels, small sea cucumbers or other ascidians, covering them completely and killing them. Botrylloides violaceus has completely replaced Botrylloides leachii, the autochthonous ascidian in this area. Both species of ascidians compete for the same substrate. Cycloporus papillosus preys on Botrylloides violaceus and places its egg plates (Fig. 1D) in the folds of this species (in the area where new zooids grow and extend the colony) or under the unattached colony, thereby ensuring larval protection and the availability of food after hatching.

In Galicia, three specimens of Cycloporus papillosus were captured from mussels collected on Botrylloides violaceus on the docks of the Yacht Club Ribeira (Ria de Arosa, Galicia, Spain). Depth varied between 0.5 and 1 metres (42°33.7770N, 008°59.2970W; 42°33.7850N, 008°59.3140W; 42°33.7930N, 008°59.3290W). Another specimen (Figure 1B) was collected on a colony of Botryllus schlosseri (Ascidiacea) growing on a rock of the island of Rua (Ria de Arosa, Galicia, Spain), at a depth of 14 metres (42°32.9650N, 008°56.4590W).

This is the southernmost European record for Cycloporus papillosus, and the first for the Atlantic coast of the Iberian Peninsula. Other localities from where this polyclad has been reported are: Bergen, Norway (Jensen 1878); Rovigno, Croatia (Vàtova 1928); Susaki near Simoda, Japan (Kato 1937); Porto Praia, Cape Verde (Laidlaw 1906); Plymouth, United Kingdom (Gamble 1893).

Two mature specimens captured during winter 2012 (15/01/2012). Voucher: one specimen sectioned sagittally, stained with Azan and deposited in the Invertebrate Collections of the MNCN; Cat. Nr: MNCN 4.01/626 to 4.01/647 (22 slides).

Captured worms 10 mm long and 5 mm wide. Body shape elongated, with straight margins. Dorsal surface smooth. Background coloration of the dorsal surface pale brown, translucent, with dark branched bands, red or brown, depending on intestinal contents, (Figure 2A). Ventral side pale yellow without bands. With narrow conical marginal tentacles; sucker slightly posterior to the middle of the bodies. Tentacular eyes at the base of the tentacles (Figure 2C) and cerebral eyes in two elongated clusters, sometimes extending over the pharynx. Tubular, whitish pharynx is visible at the anterior end (Figure 2C).

Male copulatory apparatus located posterior to male pore and directed forwards (Figure 2D). Prostatic vesicle oriented antero-dorsally, with a smooth glandular epithelium, and directly connected to tubular stylet of penis papilla. Seminal vesicle empties through a narrow short duct into distal end of prostatic vesicle. Female pore lies closely behind male pore, but is clearly separated. Female atrium elongated. Cement pouch rounded and followed by a short vagina and opening of uteri. A pair of uterine vesicles is present.

Eurylepta cornuta shows two varieties: 1. Eurylepta cornuta var. lobianchi, first described by Lang (1884) and known from the Mediterranean Sea, and 2. Eurylepta cornuta var. melobesiarum, first described by Schmidtlein (1880) as Proceros melobesiarum. The main difference between these varieties is in the arrangement of the cerebral eyes (Lang 1884; Bock 1913). In Eurylepta cornuta var. melobesiarum the elongated patches are shorter than in Eurylepta cornuta var. lobianchi. Therefore, and in agreement with other authors (e.g., Micoletzky 1910; Bock 1913; Faubel 1984), we consider the difference not enough to maintain the two varieties and propose that should no longer be recognized.

Eurylepta cornuta was found in empty shells of Mytilus galloprovincialis (Figure 2A), which were attached to mussel culture ropes suspended from specially designed rafts called “bateas”, located in La Palmeira (Ria de Arosa, Galicia, Spain) at a depth of 13 metres (42°34.3910N, 008°56.6360W). Several specimens of Eurylepta cornuta (Figure 2B) were also captured for the first time within Saccorhiza polyschides stipes (macroalgae), at a depth of 8 metres in “Cuberto Camouco” (Ria de Arosa, Galicia, Spain) (42°33.4150N, 008°57.8390W). Another specimen was found under a stone on the island of Rua, at a depth of 14 metres (42°32.9200N, 008°56.4220W).

Eurylepta cornuta has been known since the 18^th century from Kristiansand, Norway (O.F. Müller 1776) and since the 19^th century from Belfast Bay, Ireland (Thompson 1845); Saint Malo, France (Keferstein 1868); Plymouth Sound, United Kingdom (Gamble 1893); and the Gulf of Naples, Italy (Lang 1884).

One specimen captured during winter 2012 (09/12/2012).

Holotype. One sagittally sectioned specimen, stained with Azan and deposited in the Invertebrate Collections of the MNCN; Cat. Nr. MNCN 4.01/502 to 4.01/572 (71 slides).

Ribeira (Ria de Arosa, Galicia, Spain). Depth; 5 metres (42°33.7760N, 008°59.3390W).

Living elongated worms 25 mm long and 14.4 mm wide. Body shape broad, slightly oval and with undulating margins. Colouration in living animals yolk yellow (Figure 3A, B); fixed individuals have a transparent look; with small dark patches representing the uterine network over entire body surface (Figure 3C). Ventral side pale yellow. Marginal tentacles well-developed, conical. Sucker posterior to middle of the body. Tentacular eyes on the dorsal margin of tentacles (Figure 3D), marginal eyes in two small clusters on anterior margin (Figure 3E) and cerebral eyes in two elongated anteriorly anastomosing clusters (Figure 3E). Tubular pharynx near anterior end; oral pore closely posterior to brain. Male and female genital pores clearly separated, anterior and ventral to the pharynx, respectively (Figure 3F).

Male copulatory apparatus located posterior to the male pore and directed forwards (Figure 3G, H). Male system consists of a small penis papilla with a short stylet, a true prostatic vesicle with a smooth glandular epithelium and an elongated seminal vesicle. Prostatic vesicle is oval and small, and opens directly into the penis papilla, which projects into the male atrium. Seminal vesicle empties into distal end of prostatic vesicle through a long, narrow ejaculatory duct. Characteristic spermiducal vesicles open proximally into seminal vesicle.

Small female system is difficult to distinguish except for uterine network and well developed cement glands. Female pore lies behind male pore and is clearly separated from it. Vagina shows a small expansion (or cement pouch; cf Hyman 1953), ascends dorsally and subsequently splits into two uteri. Uteri extend as a uterine network with channels that connects to the ovaries. Uterine vesicles absent.

Based on the presence of the conical marginal tentacles, the spermiducal vesicles, an armed penis and a uterine network, this new species belongs to the genus Euryleptodes Heath & McGregor, 1912 of the family Euryleptidae Lang, 1884. The genus Euryleptodes presently comprises of two species: Euryleptodes cavicola Heath & McGregor, 1912 and Euryleptodes insularis Hyman, 1953, both from California.

Euryleptodes galikias sp. n. differs from Euryleptodes insularis in the long ejaculatory duct, the tentacular eyes over the tentacles, and the frontal marginal eyes.

Compared to Euryleptodes cavicola, which has a long stylet, the stylet of Euryleptodes galikias is short. Furthermore, Euryleptodes cavicola lacks spermiducal vesicles, thus distinguishing it from both Euryleptodes galikias and Euryleptodes insularis.

Differences in colouration are also apparent between the species: yolk yellow in Euryleptodes galikias sp. n., greenish white in Euryleptodes cavicola, and brown with dark spots in Euryleptodes insularis. Lastly, the pattern of distribution is vastly different, with Euryleptodes galikias off the eastern coast of the North Atlantic Ocean (Spain), while the other two species occur off the eastern coast of the North Pacific Ocean (California).

Euryleptodes galikias sp. n. was found within empty shells of Mytilus galloprovincialis, which were attached to a boat anchor on the third dock of the Yacht Club Ribeira (Ria de Arosa, Galicia, Spain), of a depth of 5 metres (42°33.7760N, 008°59.3390W).

Two specimens captured in winter 2010 and 2012 (15/03/2010 and 24/02/2012). Voucher: one specimen sectioned sagittally, stained with Azan and deposited in the Invertebrate Collections of the MNCN; Cat. Nr: MNCN 4.01/648 to 4.01/662 (15 slides).

Elongated worms 10–30 mm long and 7–15 mm wide. Body shape elongated, leaf-shaped, with pointed anterior and posterior ends, and with light undulating margins. Marginal tentacles well developed with whitish edges and pointed ends. Dorsal surface smooth. Background coloration whitish or ivory, with black, continuous stripes; between the stripes, black discontinuous lines are present (Figure 4C). Faint white band runs along the entire body margin (Figure 4A, B). Ventral side smooth and pale. Sucker in middle of body or slightly more posterior (Figure 4E). Cerebral eyes form two compact elongated, frontally anastomosing groups (Figure 4A). Tentacular eyes scarce and mainly at base of tentacles. Tubular pharynx near anterior end, oral pore in posterior region first quarter of the body. Male and female genital pores clearly separated and located behind the pharynx (Figure 4D, E).

Male copulatory apparatus with antero-dorsally oriented prostatic vesicle (Figure 4D, E). Male system consists of a short penis papilla armed with a small conical stylet, a true prostatic vesicle with a smooth glandular epithelium and a seminal vesicle with a thick muscle layer. Vasa deferentia join a dilated common vas deferens that opens into seminal vesicle. Copulatory complex lies forwardly oriented, and seminal vesicle opens through a small duct directly into distal end of prostatic vesicle.

Female system lies posterior to male pore and is characterized by a short, rounded female atrium and a cement duct or pouch. In our specimen, a second dilatation (so-called shell gland pouch) follows the atrium, into which shell glands open. Posteriorly-orientated vagina and numerous uterine vesicles are situated medially to this pouch.

Prostheceraeus vittatus feeds mainly on Clavelina ascidians, as other Prostheceraeus species (Figure 4B).

Lang (1884) mentions in the original description that specimens less than 1.5–2 cm in length were immature. However, sometimes our specimens from the Atlantic coast were mature, despite their small size (c. 1.5 cm in length).

Two specimens of Prostheceraeus vittatus were captured during this study. The first animal was collected from “A Tiñosa” (Ria de Arosa, Galicia, Spain) on a rocky bottom between Clavelina lepadiformis colonies, at a depth of 24 metres (42°32.8240N, 008°57.9920W). The other worm was found on stones in “Petón Bajo” (Ria de Arosa, Galicia, Spain), at a depth of 16 metres (42°32.9880N, 008°57.9920W).

Prostheceraeus vittatus is known from the North Atlantic coasts of the United Kingdom, France, Ireland, Scandinavia, Norway, Denmark, from the Mediterranean shores in Italy (Gulf of Naples) (Faubel and Warwick 2005) and Spain (Catalonia) (Novell 2003). This is the first record for the species from the North Atlantic side of the Iberian Peninsula.

Two specimens captured during the spring of 2010 (07/06/2010). Vouchers: one specimen sectioned sagittally, stained with Azan and deposited in the Invertebrate Collections of the MNCN: Cat. Nr: MNCN 4.01/663 to 4.01/688 (26 slides); one specimen sectioned sagittally, stained with Azan and deposited in the Invertebrate Collections of the MNCN: Cat. Nr: MNCN 4.01/689 to 4.01/731 (43 slides).

Elongated worms 1–1.5 cm long and 0.5–0.7 mm wide (Figure 5A, B, C). Body shape elongated, wider at the posterior end, with light undulating margins and rounded anterior and posterior ends. Marginal tentacles with characteristic purple pigment. Dorsal surface smooth. Dorsal colouration whitish or yellowish, with dark, rounded spots and a yellow band along the body margin; at times background pigmentation faintly orange or pinkish (Figure 5A, B). Ventral side smooth and pale. Sucker approximately in middle of body. Tentacular eyes scarce and scattered over tentacles; cerebral eyes inconspicuous, in two elongated rows. Plicate cylindrical or tubular pharynx near anterior end, oriented frontally; oral pore behind brain. Male and female genital pores clearly separated and behind pharynx (Figure 5H).

Male copulatory apparatus perpendicular to male pore (Figure 5D, G, H). Male system consists of a short penis papilla, armed with a small conical stylet, a true prostatic vesicle with a smooth glandular epithelium, and a seminal vesicle with a thick muscle layer. Vasa deferentia, sometimes very dilated, join an expanded vas deferens (possibly an external seminal vesicle; Figure 5F, G) before opening directly into true seminal vesicle. Prostatic vesicle opens at tip of penis papilla and seminal vesicle opens through a duct into distal end of prostatic vesicle.

Female system (Figure 5D, E) lies posterior to male pore and is characterized by a short, rounded female atrium, a cement duct or pouch, followed by a second dilatation of atrium and a posteriorly-orientated vagina. Cement and shell glands empty into cement duct.

Prostheceraeus moseleyi feeds mainly on Clavelina lepadiformis (Ascidiacea) (Figure 5B, C).

Faubel (1984) considers Prostheceraeus moseleyi as a species incertae sedis because in the original description by Lang (1884) the uterine vesicles were not mentioned. In our specimens, multiple uterine vesicles (Figure 5D, E) run along both sides of the main body axis and therefore, Prostheceraeus moseleyi can now be considered as a valid species of the genus Prostheceraeus.

Specimens of Prostheceraeus moseleyi were collected from the bottom of the pier at the Yacht Club Ribeira (Ria de Arosa, Galicia, Spain) at a depth of 5 to 10 metres (42°33.7410N, 008°59.3380W). This species was recorded from Italy (Gulf of Naples, Lang 1884) and Spain (in several localities of the coast of Catalonia, Novell 2003). Our sample represents the first record for the Atlantic coast and outside from the Mediterranean Sea.

Two specimens collected in winter 2012 (09/01/2012). Voucher: one specimen sectioned sagittally, stained with Azan and deposited in the Invertebrate Collections of the MNCN Cat. Nr: MNCN 4.01/732 to 4.01/744 (13 slides).

Mature, elongated specimens 10–18 mm long, occasionally as long as 30 mm, and 4–6 mm wide. Body shape long and narrow, sometimes with a little fan-like expansion at the anterior end, straight margins, rounded anterior and tapered posterior end. Without tentacles. Dorsal surface smooth. Dorsal colouration beige to yellow, without spots or bands (Figure 6A, B). Ventral side smooth and pale. Sucker in the middle of the body or slightly anterior. Cerebral eyes arranged in two slightly curved rows; marginal eyes along the anterior edge; young individuals have an eye-free medial area. Well-developed plicate tubular pharynx located near the anterior end, oriented frontally; oral pore closely behind the brain. Male and female genital pores separated and located posterior to pharynx (Figure 6C).

Male system consists of a short penis papilla armed with a conical, Arabian dagger-like stylet an anterior orientated seminal vesicle and two spherical prostatic vesicles with a smooth glandular epithelium covered with a thick muscle layer. Vasa deferentia open separately into a seminal vesicle. Ejaculatory duct and prostatic ducts very long and spiral-shaped; prostatic ducts meet at proximal end of small penis papilla. Male atrium elongated and conical (Figure 6D).

The female system lies posterior to male pore and is characterized by a short, spindle-like female atrium, a cement gland pouch, followed by a backwards orientated vagina, and backwards directed uteri.

One specimen was found in mussel samples collected from the floats of the third dock of the Yacht Club Ribeira at a depth of 1 metres (42°33.7700N, 008°59.3260W). The other animal was collected from under a rock in the area “A Ameixida” at a depth of 6 metres (42°32.2490N, 008°59.1640W). Prosthiostomum siphunculus is known from the western European Atlantic coasts, the Mediterranean and the Tyrrhenian Sea, and also from North and South Africa, Somalia and Vietnam (Prudhoe 1985).