22 



Genus 5. TROCHITA, Schumacher. 



Animal ; similar to that of Calyptraea. 



Shell ; conical, sometimes inclining to spiral ; internal appendage 



somewhat lateral and effused, sometimes trochoid, reaching to 



the margin. 



In this genus the internal appendage takes the form of a spiral septum 

 of trochoid growth. In some species, as in T. radians, spirata, and cly- 

 peolum the appendage reaches to the margin ; in others, as in T. conica, 

 subreflexa, and Sinensis, the appendage is comparatively small, lateral, and 

 effused. The last constitute Dr. Gray's genus Galerus. 



The western coasts of South and Central America and Australia are the 

 principal habitats of this genus. One species, T. Sinensis, is found in 

 Britain, but only as a straggler on the southern shores. 



1. aspersa, C. B. Adams. 



2. Calyptraeformisj Lam. 



3. clypeolum, Reeve. 



4. conica, Brod. 



5. corrugata, Reeve. 



Species, 



6. lichen, Brod. 



7. macnlata, Q"o>/. 



8. inainillaris, Brod. 



9. pellucida, Reeve. 

 10. poculuin, id. 



11. radians, Lam. 



12. Sinensis, Linn. 



13. solida, Reeve. 



14. spirata, Forbes. 



15. subreflexa, Carp. 



Genus 6. CREPIDULUM, Lamarck. 



Animal ; similar to that of Calyptraea. 



Shell ; ovate or oblong, gradually oblique, smooth exteriorly, rarely 

 ribbed, with the apex mostly marginal and more or less beaked, 

 interiorly holloio, with a horizontal deck-like lamina, sometimes 

 notched at the side. 



The Slipper Limpets are of a more oblong form than the Cup-and-Saucer 

 Limpets, and the internal appendage takes the form of a transverse deck. 

 The species are prettily marked, and mostly smooth, but there are one or 

 two very beautiful exceptions ; C. costata and aculeata are ribbed and 

 densely beset with prickles, whilst in C. Lessonii the shell is disposed in a 

 series of delicately fringed laininae. 



They are chiefly inhabitants of the New World. 



