402 MOLLUSCA. 



fall together ; in this way small marine animals are seized and drawn into 

 the mouth. 



Faru. 1. Atlantidae. Visceral sac and shell coiled in a spiral. The 

 metapodium carries an operculum. Atlanta Lesueur. 



Fam. 2. Carinariidae. Visceral sac and shell conical, and small in relation 

 to rest of body; foot elongated, without operculum. Carinaria Lam. 



Fain. 3. Pterotracheidae. Visceral sac reduced ; without mantle and shell ; 

 a sucker on foot in male only. Pterotrachea Forskal. No tentacles ; a filiform 

 appendage at posterior part of foot. Firoloida Lesueur. Tentacles present ; 

 gill and posterior pedal appendage absent. 



Tribe 5. GYMNOGLOSSA. 



Radula and jaws absent. 



Fam. 1. Eulimidae. Proboscis elongated; tentacles without furrow; often 

 parasitic on Echinoderms. Shell small, long, subulate, polished. Eulima 

 Risso; StiUfer (Stylifer] Brod., a cephalic pseudopallium extending over shell, 

 in body-wall of male star-fish. 



It is convenient to place here the two genera Entocolax and Entoconcha, both 

 parasitic on Echinoderms. In these genera there is only a vestige of the 

 alimentary canal with a single opening. The visceral mass is surrounded by 

 the pseudopallium, and the cavity so formed receives the generative duct and 

 opens to the exterior by a small orifice. Entocolax Voigt. Fixed by the 

 aboral extremity ; sexes separate. E. Ludwigi, fixed to the body-wall in body- 

 cavity of a Holothurian. Entoconcha Miiller, vermiform, fixed by the oral end ; 

 hermaphrodite. Larva with a shell (resembling that of NaMca), operculum and 

 velum. E. mirabilis Miiller, in body-cavity of Synapta digitata attached to 

 intestinal wall. 



Order 2. EUTHYNEURA.* 



Hermaphrodite Anisopleura, in which tlie visceral commissure is 

 not twisted (save in the Actaeonidae). The primitive left gill, 

 nephridium, and auricle are always aborted, and the operculum is 

 generally absent. 



There are typically two pairs of tentacles on the head. The vis- 

 ceral commissure is generally very short, and its ganglia (Fig. 316) 



* Alder and Hancock, "A Monograph of the British Nudibranchiate Mollusca," 

 London, 1845-55. Hancock, "On the Anatomy of Doridopsis," Trans. Linn. 

 Soc. London, 25, 1865. H. Lacaze Duthiers, "Anat. et Phys. du Pleurobranche 

 orange," Ann. Sci. Nat. (4), 11, 1859. Id.,"Du system e nerveux des Mollusques 

 gasteropodes pulmones aquatiques," Arch. Zool. Exp. (1), 1, 1872. Id., "Histoire 

 de la Testacelle," ib. (2), 5, 1887. Vayssiere, "Recherches zoologiques et 

 anatomiques sur les mollusques Opisthobranches du Golfe de Marseille," Ann. 

 Mus. Marseille (Zool.}, 2 and 3, 1885-88. P. Pelseneer, " Report on the 

 Pteropoda," Challenger Reports, pt. 66, 1888. Bergh, "Die kladohepatischen 

 Nudibranchier," Zool. Jahrb. (Abth. f. System.), 5, 1890. Leicly, "Special 

 Anatomy of the terrestrial Gastropoda of the U.S." in Binney, The terrestrial 

 air-breathing Molluscs of the U.S., vol. i. , Boston, 1851. P. Pelseneer, 

 " Recherches , sur divers Opisthobranches," Mtmoires Couronnes et Memoires 

 des Savants Strangers, Acad. Bruxelles, 53, 1894. L. Pfeiffer, " Monographia Heli- 

 ceorum Fiventium," Leipzig, 1848-69 ; and Monographia Auriculaceorum 

 Viventium, Cassel, 1856. A. Rossmassler, " Iconographie der Land-u. Siissivasser 

 Mollusken Europas, Leipzig, 1835-59. Ferussac et Deshayes, Hist. nat. gen. 

 ft partic. des Mollusques terrestres et fluviatiles, Paris, 1829-51. 



