GASTEROPODA. 127 



^hell, hyaliue, globular or subulate, apex tapering, stylifomi, nucleus 

 sinistral. 



Animal with slender, cylindrical tentacles, and small sessile eyes at tkeii 

 outer bases ; mantle thick, reflected over the last whirls of the shell ; foot 

 large, with a fi-outal lobe. Branchial plume single. Attached to the spines 

 of sea-urcliins, or immersed in living star fishes and corals. 



Distr., 6 sp. W. Indies, Brit., Philippines, Gallapagos. 



LoxoNEMA, Phillips. ^ 



Etym., loxos, oblique, and nema, thread ; in allusion to the striated sur- 

 face of many species. 



Shell elongated, many-whiiied ; apertni-e simple, attenuated above, effused 

 below, mth a sigmoidal edge to the outer lip. 



Fossil, 75 sp. L. silm'ian — Trias. N. America, Em-ope. 



Maceocheilus, Phillips. 

 Et'i/m., macros, long, and cheilos, lip. 



Shell, thick, ventricose, buccinoid ; aperture simple, effuse below ; outer 

 lip thin, inner lip wanting, columella callous, slightly tortuous. 

 Type, M. arculatus, Schlotheim sp. Devonian. Eifel. 

 Fossil, 12 sp, Devonian — Carboniferous. Brit., Belgium. 



FAMILY III. Cemthiad^. Cerites. 



Shell spiral, elongated, many- whirled, frequently varicose;. aperture chan- 

 nelled in front, with a less distinct posterior canal ; Up generally expanded 

 in the adult ; operculum horny and spiral. 



Animal with a short muzzle, not retractile ; tentacles distant, slender ; 

 eyes on short pedicels, connate with the tentacles; mantle-mai'gin with a 

 rudimentary siphonal fold; tongue armed with a single series of medijui 

 teeth, and three laterals or uncini ; marine, estuary, or fresh-water. 



Cerithium (Adans.), Bruguiere, 



Etyni,, ceration, a small horn. 



Type., C. nodulosum. PI. VIII., fig. 16. 



Shell turreted, many-whirled, with indistinct varices; aperture small, 

 with a tortuous canal in front; outer lip expanded; inner lip thickened. 

 Operculum horny, paucispiral. PI. VIII., fig. 16*. 



Bisir., above 100 sp. World-wide, the typical species tropicaL Norwiiv, 

 Brit, Medit., W. Indies, India, Australia, China, Pacific, Gallapao'os. 



Fossil. 460 sp. Trias — . Brit., Prance, U. States, &;c. 



Sub-genera. Rhinoclavis, Sw. C. vertagus. Canal long, bent abruptlv ; 

 operc., sub-spiral. 



Bittium, Leach. C. reticulatimi, PI. VIIL, fig. I7. Small northern 

 species, ranging from low-water to 80 fathoms. 



