230 Lamarck's Genera of Shells. 



Shell pointed, conical, striated ; vertex curved, involute ; 

 aperture widest in the transverse direction, internally rose- 

 coloured. 



Mediterranean. Pl. VII. Fig. 118. 10 Species. 



5. Calyptrsea. 

 Animal unknown. 



Shell conoidal, vertex erect, imperforate, subacute ; base 

 orbicular. Cavity furnished with an attached, convolute la- 

 mina, or spiral diaphragm. 

 Type. Calyptrcea equestris*. (Patella equestris. Linn.) 



Shell suborbicular, convex-conical, thin, pellucid, white, with 

 acute, xmdulated, subtuberculated, longitudinal strise, increasing 

 in size towards the margin ; vertex subacute, curved. Indian 

 Ocean. PI. VII. Fig. 119. 



6. Crepidulat. 



Animal head forked anteriorly. Two conical tenta« 



cula, with eyes at their external base. Mouth simple, without 

 jaws, and placed at the bifurcation of the head. Branchia 

 single, subpenicillate, projecting beyond the branchial cavity, 

 on the right side of the neck. Mantle never extending beyond 

 the shell. Foot very small. Anus lateral. 



Shell oval or oblong, convex externally, internally concave ; 

 spire very much inclined towards the margin ; aperture partly 

 closed by a horizontal lamina. 



The shell of the crepidula not only covers the animal, but 

 partly ensheathes it, for the chamber, formed by the lamina, 

 always contains a portion of its body. It has no operculum. 

 Found on rocks near the sea-side. 



Type. Crepidula fornicataX. (Patella fornicata. Linn.) 



Shell oval, posteriorly obliquely curved ; posterior lip concave. 



Barbadoes. PI. VII. Fig. 120. 6 species. 

 7. Ancylus§. 



Body creeping, wholly covered by the shell. Two com- 



* Equestrian. Lamarck's third species. His type is C, extinctorium. 



t Dim. from crepida, % little siioe. 



t Arched. 



^ Is this a corruption of ancile or ancilium, a sacred shield '! We can find 

 no such word as ancylus. But this is not the only instance in which our 

 author's Latin names are somewhat diflScult to translate. 



