30 CRANIA. 
COR'DIFORM. Oe aheart.) Heart-shaped, applied gene- 
rally to any shell which may be fancied to resemble a heart in 
shape, as Isocardia, fig. 126, and Cardium Dionzum, fig. 122. 
CORNEA. Megerle. Cycras, Lam. 
COR'NEO-CALCA’REUS. A term used to express the mix- 
ture of horny and calcareous matter, which enters into the com- 
position of some shells; Aplysia, for instance. It is also applied 
to those opercula which are horny on one side, and testaceous 
on the other, as that of Turbo. 
CORNEOUS. Horny. A species of Patella has the specific 
name corneus given to-it, because its texture more nearly re- 
sembles that of a horn than that of ashell. The epidermis of 
freshwater shells is of a similar composition. 
CO’RONATED. (Corona, crown.) Applied to shells when 
ornamented with a series of points, tubercles, &c. round the 
upper edges of their volutions. Ha. Conus Nocturnus, fig. 459. 
CORON'ULA. (Corona, crown, dim.) Order. Sessile Cirri- 
pedes, Lam. Fam. Balanidea, Bl. Deser. Six radiated valves, 
articulated side by side, in a circle, forming a depressed cone ; 
internal structure of the valves, porous or camerated, thickened 
at the base; aperture closed by four valves in pairs; imbedded 
horizontally ina cartilaginous substance. Obs. The shells com- 
posing this genus are found partly imbedded in the skin of 
whales, and the shell of tortoises, and are therefore destitute of 
the shelly bases which support the Balani and other Coronular 
Multivalves. C. Testudinaria, (CHELONOBIA, Leach,) fig. 15. C. 
Balenarum, (Cxropirus, Ranz,) fig. 16. C. Diadema, (Dis- 
pEMA, Ranz.) Fig. 17. 
CORRO'DED. (Corrodo, eat away, consume.) The umbones, 
apices and other thick parts of shells are frequently worn away or 
consumed by the chemical action of the element in which they 
exist. As the thickest parts of some shells are the most subject 
to this operation, it appears to me to arise from the outer surface 
of the shell being less under the influence of the animal juices, 
than the inner surface, and therefore more exposed to the action 
of the circumambient element. This, however, cannot be the 
case with respect to the Nayades and some other fresh water 
shells; with these, corrosion does not take place until after the 
thick epidermis which covers them, becomes wounded by some 
means or other, and then the animal thickens its shell within as 
fast as it is corroded without. 
COW’RY. A common name for shells of the genus Cyprea. 
CRANIA. Retz. (Cranium, a skull.) Fam. Rudistes, Lam. Order. 
Palliobranchiata, Bl. Descr. Inequivalve, generally equi- 
lateral, irregular, subquadrate; upper valve patelliform, conical, 
with the umbo near the centre; lower valve attached by its 
outer surface. Muscular impressions four in each valve; two, 
