REMARKS ON THE GENUS SCISSUKELLA. 385 
cently instituted in France, under the title Scissurella. An 
abstract of the paper, announcing the genus, by M. Alcide 
Dessahnes D'Orbigny, in Memoires de la Societe d'Histoire 
Naturelle de Paris, i. 340, is given by Mr G. B. Sowerby 
in the Zoological Journal, i. 255. 
M. D'Orbigny's character of the genus, as translated by 
Mr Sowerby, stands thus: " Shell univalve, free, umbili- 
cated, with a depressed spire, aperture rather rounded, 
without a canal, its lips without a peristome and disjoined : 
right lip notched with a deep slit, following the growth of 
the volutions, obliterated to v/ithin a short distance of the 
margin, and forming a sort of keel upon the back of the 
shell."" According to M. D'Orbigny, the shell belongs to 
the family of Trochidse, while Mr Sowerby is inclined to 
consider it as related to the Fissurellad^. The last ob- 
server supposes that the slit in maturity is obliterated at 
the margin, leaving the peristome entire ; but that imme- 
diately behind the margin, there is a perforation left by a 
portion of the slit not being filled up, as in the genus Hali- 
otis. Though this last circumstance may take place in 
some species, I may observe, that in the one in my posses- 
sion, that part of the body whorl on each side the slit is 
apt to break off, and thus efface the most obvious mark of 
the genus. 
Scissurella crispaia.-^SheW white^ and without an 3^ ap- 
parent cuticle. The largest specimen in my possession 
does not equal the fifteenth of an inch. Whorls three, in- 
creasing rather rapidly from the slightly elevated apex, and 
sloping with a gentle convexity from the separating hne to 
the keel. Under side with a central cavity, from which the 
whorl extends, a little convex, to the keel. The whorls are 
marked by numerous fine transverse arcuated ribs, narrower 
than the intervening spaces, crossed by fine longitudinal striae 
VOL. VI. B b 
