OF MOLLUSCA. 157 



serrated. Foot very narrow, with a long beard on each side in front ; 

 lateral fringe with three ciliated beards on each side. Operculum 

 orbicular, horny, of six or eight whorls. Penis on right side in front 

 of neck-lobe ; vent further back on same side. 



The right neck-lappet of Trochus is always larger than the left, 

 which, however, is also bifid, but plain, and never ornamented, fringed 

 or serrated, as is sometimes seen on the right one, as for instance in 

 Vitrinella divisa. — Clark, Moll. 516. 



The male organ of Vitrinella Cutleriana is a rather long, flat, 

 smooth filament, horizontally exserted, close under the right tenta- 

 culum. — Clark, Moll. 319. 



The animal of Vitrinella Cutleriana only differs from that of 

 V. serpuloides in the cilia on the tentacula and vibracula being more 

 sparse, and the foot less auriculated in front. The operculum of 

 three or four lax whorls. — Clark, Moll. 316. 



The animal and operculum of Vitrinella nitens are equally similar 

 to the other two. — Clark, Moll. 316. 



26. Valvatella. 



Shell conic ; whorls rounded, with laminar periostraca , axis m- 

 perforate; aperture circular; peristome simple. Operculum cir- 

 cular, horny, many whorls. 



1. V. Grcenlandica. 



d. Shell subturrited, smooth, polished ; aperture subovate, rather 

 elongate; whorls laterally compressed; pearly coat greenish ; 

 axis imperforate. Canthiridina. (Pages 147, 155.) 



27. Canthiridus. 



Shell ovate, conical ; spire conic ; whorls slightly keeled ; pillar 

 with a small tooth in front ; outer lip entire ; throat smooth. 

 Operculum circular. 



1. C. iris. 



2. C. purpuratus. Operculum circular, of many whorls. 



3. C. Zealandicus. Operculum circular, of many whorls. 



28. Elenchus. 



Shell conical, turrited, smooth, polished; whorls rounded; axis 

 imperforated ; aperture ovate, longer than wide ; throat pearly ; 

 pillar-lip with a tooth in front ; outer lip thickened and grooved 

 internally. Operculum circular. 



I. E. irisidontes, t. 125. f. 8. Operculum circular, smooth. 



Teeth 00 • 5 • 1 • 5 • 00 ; the fifth or outer central teeth large ; the 

 hooks denticulated ; the lateral teeth hooked, the first denticulated 

 (fig. 84). 



