264 PATELLIDJE. 



CALYPTR^EA AND PILEOPSIS. 



A few general remarks on Calyptr&a and Pileopsis, the two 

 remaining genera of this tribe, may not be unsuitable before 

 their specialties are noticed : each has only a single British 

 species ; their shells, with the addition of minute spiral apices, 

 have the symmetrical patelloid figure, and a like crescent- 

 shaped muscular cicatrix. The animal appears, essentially, 

 similar to the Patella : there is only a single branchial 

 plume ; their inaptitude for locomotion is accordant, nay, even 

 more rigid ; the deep marginal sinuosities of their testaceous 

 cones show that they adapt their growth to the inequalities of 

 the substances on which probably the germs are cast ; the 

 only movement seems confined to the elevation and depression 

 of the shell, to receive the ambient element ; they possess the 

 same apparent hermaphroditism as their allies, and prove that 

 this system of sexuality is the concomitant of apathy and a 

 less developed organization. Calyptr&a, from its symmetry, 

 organs and habitudes, appears almost congeneric with Pile- 

 opsis , and a well-established member of the Limpet family ; 

 still, some malacologists have doubts as to its natural position, 

 which arise from the singular internal rudimentary subspiral 

 lamina. I almost think it is properly placed, and that the 

 appendage just mentioned is one of the evidences of a trans- 

 ition-form on the confines of a family about to pass into an 

 advanced structure and organization. 



PILEOPSIS, Lamarck. 

 P. HUNGARICUS, Linn, et Auct. 



P. hungaricus, Brit. Moll. ii. p. 459, pi. 60. f. 1,2 (as Capulus] ; (ani- 

 mal) pi. C. C. f. 5. 



Animal inhabiting a rough, irregular, subconical shall, with 

 a minute spirally-twisted posterior vertex, from which striae of 

 various sizes radiate to the basal periphery ; it is clothed with 

 a thin caducous epidermis, and in the interior some examples 

 exhibit a brilliant porcellanous white, and others the variable 



