GASTEBOPODA. 241 



Animal with a long retractile proboscis ; tentacles close 

 together, slender, inflated at the tips ; eyes immersed at the 

 bases of the tentacles ; operculum lobe ample, unsymmetrical ; 

 foot truncated in front. Eanges to 80 fathoms water. 5 British 

 species, Norway. 



Fossil. ? species. Pliocene — . Britain (Crag). 



Styloptygma, Adams. 1860. 



Shell pupiform, semi-transparent; with slightly convex whorls. 

 Aperture sub-quadrate. 



Myonia, Adams. 



Shell ovate, turreted ; white, thin, with slightly convex 

 whorls. Aperture oblong. 



Leucotina, Adams. 



Shell like last, but with last whorl ventricose ; with minute 

 dots. 



Stilifer, Brod. 



Example, S. astericola. PI. YIII., Fig. 15. 



Synonym, Stylina, Fleming. 



Shell hyaline, globular or subulate, apex tapering, styliform, 

 nucleus sinistral. 



Animal with slender, cylindrical tentacles, and small sessile 

 eyes at their outer bases ; mantle thick, reflected over the last 

 whorls of the shell ; foot large, with a frontal lobe. Branchial 

 plume single. Attached to the spines of sea-urchins, or immersed 

 in living star- fishes and corals. 



Distribution, 16 species. West Indies, Britain, Philippines, 

 Gallapagos, Pacific. 



LoxoNEMA, Phillips. 



Etymology, loxos, obUque, and nema, thread ; in allusion to 

 the striated surface of many species. 



Type, L. sinuata, U. Devonian, Petherwin. 



Shell elongated, many-whorled ; aperture simple, attenuated 

 above, efi'used below, with a sigmoidal edge to the outer lip. 



i^oss/?, 75 species. L. Silurian — Trias. North America, Europe. 



Macrocheiltjs, Phillips. 



Etymology, macros, long, and cheilos, lip. 



Synonym, Polyphemopsis, Portlock. 



Shell thick, ventricose, buccinoid; aperture simjle, effuse 



