949 MANUAL OF THE MOLLUSCA. 
below; outer lip thin, inner lip wanting, columella callous, 
slightly tortuous. 
Type, M. arculatus, Schlotheim species. Devonian. Hifel. 
Distribution, 1 species (M. Japonicus), Korea Straits. 
Fossil, 12 species. Devonian— Carboniferous. Britain, 
Belgium. 
Faminy IJJ.—CERITHIADZ. Cerites. 
Shell spiral, elongated, many-whorled, frequently varicose ; 
aperture channeled in front, with a less distinct posterior canal ; 
lip 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-margin with a rudimentary siphonal fold; tongue 
armed with a single series of median teeth, and three laterals 
or uncini. Mr. Wilton has examined the dentition of four 
Cerithiade ; the teeth are broad, as in Melaniade, with incuryed 
and dentated summits. In Cerithidiwm the median teeth are 
slender with minute hooks. Habitat. Marine, estuary, or fresh 
water. 
CERITHIUM (Adans.), Bruguiere. 
Etymology, ceration, a small horn. 
Type, C. nodulosum. Pl. VIII., Fig. 16. ‘ 
Shell turreted, many-whorled, with indistinct varices; aper- 
ture small, with a tortuous canal in front; outer lip expanded ; 
inner lip thickened; operculum horny, paucispiral. Pl. VIII., 
Bie. 16.* 
Distribution, 136 species. World-wide, the typical species 
tropical. Norway, Britain, Mediterranean, West Indies, India, 
Australia, China, Pacific, Gallapagos. 
Fossil, 460 species. ‘Trias—. JBritain, France, United 
States, &e. 
Sub-genera. Rhinoclavis, Sw. OC. vertagus. Canal long, 
bent abruptly ; operculum, sub-spiral. 
Bittium, Leach. C. reticulatum, Pl. VIII., Fig. 17. Small 
northern species, ranging from low water to 80 fathoms. 
Triforis, Deshayes. C. perversum, Pl. VIII., Fig. 18. 30 
species. Norway—Australia. 
Fossil, Hocene—. Britain, France. 
Shell sinistral; anterior and posterior canals tubular. The 
third canal is only accidentally present, forming part of a 
varix. 
Cerithiopsis, Forbes. OC. tuberculare, Britain. 
