CAPULUS. 



Montf. 

 Pileopsis, Lam, 



TESTA oblique conica, postic^ recurva, apice 

 uncinate, sub-spirali; apertura magna, rotun- 

 dato-elliptica ; impressionibus muscularibiis 6ua- 

 bus, lateralibus, postice connatis, utraque an- 

 tice rotundata. Epidermis cornea, subvelutina. 



This Genus may be regarded as a remarkable instance of 

 the importance of a correct knowledge of the animal 

 which forms it^ as w^ell as of the characters of the shell 

 itself. We have long entertained the opinion that the 

 animal of this Genus (of which the well known Patella 

 ungarica may be regarded as the type) must be a gastero- 

 pod and consequently very different from that of De 

 France's Hipponyx, which is a truly bivalve shell. It may 

 here be observed that in the bivalve mollusca the mantle 

 envelopes tiie animal and lines the inside of the shell, 

 depositing testaceous matter on its whole internal surface ; 

 the Hipponyx is therefore a true bivalve, for its animal 

 must be wholly enveloped in its mantle, or testaceous 

 matter could not be deposited on all sides : but in the 

 present Genus, which has been very erroneously united 

 to Hipponyx by De France and Lamarck (on account, no 

 doubt, of their general resemblance in form) there is a 

 distinct head, with tentacula and eyes, and the branchia 

 are arranged in a single row behind the head, there is 

 moreover a small, nearly circular foot, by which it is 

 usually found adhering to oysters and other shells, stones, 

 &c. all which circumstances prove that it cannot produce 

 a second valve, and that it is not, therefore, even related 

 to Hipponyx. The shell itself also differs from the upper 

 valve of Hipponyx, for in Capulus it is obliquely conical 

 and curved backwards,* uncinate and somewhat spiral ; 

 in Hipponyx, however, though it is obliquely coni(;al, 



* Throughout his description of Pileopsis, Lamarck has mistaken the front 

 for the back, and vice versa. 



