CALYPTRiEA. 



sparingly covered with small muricated points, very 

 rarely spinose, sometimes with radiating striae and ribsj 

 and sometimes with nearly concentric striae. A thin 

 epidermis overlies the whole when in perfect condition, 

 but this is seldom seen in such specimens as are brought 

 into commerce. 



The Linnean Patellae equestris, Chinensis and Tro- 

 chiformis, are the types of this marine Genus, the 

 species of which are not very numerous ; they are com- 

 monly attached to large shells, stones, &c. and as they 

 generally remain stationary, they are mostly rather irre- 

 gular, and often covered witli ridges and other promi- 

 nences that are not characteristic of them, but are 

 caused by the inequalities of the surface to which they 

 have been attached, and by which their form is modified. 

 One recent species, commonly called Patella Chinensis, 

 is an inhabitant of our shores, but they are mostly 

 brought from the South Seas, and the American coasts: 

 that commonly called the cup and saucer Limpet is one of 

 the most interesting and singular, it is from the South 

 Seas: we are obliged to Mrs. Mawe for the loan of the 

 fine specimen we have figured. Among the fossils which 

 belong to tlie tertiary formations, there are two or three 

 very elegant species; the London Clay and its contempo- 

 raneous beds contain some species in great abundance. 



We have given two plates of this Genus, in order to 

 shew the several variations in form to which the internal 

 appendage is subject. 



Fig. 1. Calyptrcea deformis, Defr. a fossil from Bordeaux. 



2. 



equestris. 



3. 



Kxtinctorium ? 



4. 



spinas a. 



5. 



imbricatay Nob. 



6. 



— — Tectum Sincjise. 



7. 



spinas a y var. ? 



8. 



Pileus. Trochus Pileus, Lam. 



9. 



dilatata, Nob. 



10. 



Laumontiif a fossil species occurring in the London clay, 



and Calcaire grassier. 



