158 THE GASTROPODA 



Chenu. Shell spiral, conical, with flattened spire, umbilicatecl ; head 

 short ; tentacles split throughout their length ; foot short. Genera 

 Solarium, Lamarck. Torinia, Gray. Fluxina, Dall. FAMILY 52. 

 SCALARIIDAE, Broderip. Shell turriculated with numerous whorls and 

 an elongated spire ; head short, with a short proboscis ; foot small, 

 truncated anteriorly ; siphon rudimentary. Genera Scalaria, Lamarck ; 

 shell elongate with a circular aperture, whorls very convex, ornamented 

 with longitudinal projecting lamellae ; British. Eglisia, Gray. Crossed, 

 Adams. Aclis, Loven. 



The three following families of Taenioglossa Platypoda have neither 

 radula nor jaws, and are therefore called Aglossa. They are suctorial 

 animals with a well- developed proboscis, and are often commensal or 

 parasitic on Echinoderms ; some are abyssal. The series affords a 

 remarka'ble example of the regressive evolution of various organs as a 

 result of parasitism. FAMILY 53. PYRAMIDELLIDAE, Gray. Summit of 

 spire heterostrophic (Fig. 65, B) ; tentacles deeply grooved externally or 

 split at their extremities ; foot truncated anteriorly ; a projection, the 

 " mentum," between the head and foot ; an operculum present. 



Turbonilla scalaris, right-side view. /, foot ; in, mouth ; me, mentum ; op, operculum ; pa, 

 mantle ; sh, shell ; te, tentacle. (After Loven.) 



Genera Pyramidella, Lamarck ; columella folded, tentacles corniform. 

 Turbonilla, Leach ; columella not folded (Fig. 137). Odostomia, 

 Fleming ; columella provided with a tooth ; hermaphrodite ; British. 

 Myxa, Hedley. FAMILY 54. EULIMIDAE, Adams. Visceral mass still 

 coiled spirally ; shell thin and shining, generally with a pointed summit ; 

 tentacles without a groove. Genera Eulima, Risso ; foot well 

 developed, and with an operculum ; animal usually free, but some live 

 in the digestive canal of Holothuriae in the Fiji Islands, in the 

 Philippines, and in Europe, e.g. Eulima distorta in Holothuria intestinalis. 

 Niso, Risso. Scalenostoma, Deshayes. Hoplopteron, Fischer. Mucronalia, 

 Adams ( = Stylina, Fleming); foot reduced, but still operculate ; eyes 

 present ; animal fixed by its very long proboscis, which is deeply buried 

 in the tissues of an Echinoderm ; no pseudopallium. Stylifer, Broderip ; 

 the operculum is lost, but a rudiment of the foot remains ; tentacles very 

 small or absent ; eyes, otocysts, and a branchia present ; animal fixed by 

 a large proboscis forming a pseudopallium which surrounds the whole 

 of the shell except the more or less projecting extremity of the spire 

 (Fig. 20) ; sexes separate ; parasitic on all groups of Echinoderms in 

 different seas. Entosiphon, Koehler and Vaney ; visceral mass still 

 coiled ; shell much reduced ; proboscis very long, forming a pseudo- 



