264 PATELLID. 
CALYPTRAA anv PILEOPSIS. 
A few general remarks on Calyptrea 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 lke crescent- 
shaped muscular cicatrix. The animal appears, essentially, 
similar to the Patelle: there is only a single branchial 
plume ; their aptitude 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. Calyptrea, 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. nuNeaRiIcus, Linn. et Auct. 
P. hungaricus, Brit. Moll. 1. p. 459, pl. 60. f. 1,2 (as Capulus) ; (ani- 
mal) pl. C.C. f. 5. 
Animal inhabiting a rough, irregular, subconical shell, with 
a minute spirally-twisted posterior vertex, from which strize 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 
