42 EQUIVALVE. 
reach the border. Recent species occur in seas of all climates, 
but are not numerous. Fossil species are still more rare, ocurring 
in the Calc-grossiér, Crag and Oolite. E. fissurata, fig. 241. 
ENDOSI'PHONITES. A genus composed of Ammonites, having 
the siphon close to the body whorls. 
ENDOTOMA. Rafinesque. A genus of microscopic Foraminifera. 
ENROULEES. Lam. See Convo.urs. 
ENSIS. Schum. So.en Ensis, Auct. fig. 60, and other sword- 
shaped species. 
ENTA‘LIS. Defr. Derntatium duplicatum, Bl. PHarerrium, 
Konig? 
EN’TELLITES. Fischer. A genus composed of species of 
TEREBRATULA, SPIRIFER and Propucrus, Auct. having the 
hinge large and the umbones short. Orruis? Dalman. 
ENTIRE. (integra.) Not interrupted, not emarginated. The 
peritreme of a univalve shell is said to be entire when it is not 
interrupted by canals or by the body whorl. Ez. Cyclostoma, 
fig. 304. The palleal impression is entire, when continued with- 
out interruption, or without a sinus. 
ENTOMOSTOMATA. Bl. The second family of the order 
Siphonobranchiata, Bl. containing the genera Subula, Cerithium, 
Melanopsis, Planaxis, Terebra, Eburna, Buccinum, Harpa, Do- 
lium, Cassidaria, Cassis, Ricinula, Cancellaria, Purpura, Con- 
cholepas. 
EO'LIDES. Montf. A genus of microscopic Foraminifera. 
EPIDERMIS. (£m, epi, over or upon; depya, derma, skin.) 
The fibrous, horny, external, coating of shells, called by the 
French “ Drap marin,’ or marine cloth. Lamarck objects to 
the name Epidermis because he does not consider the substance 
as answering to the cuticle or scarf skin of the human body, but 
more analagous to the nails and hair. Gray calls it the PERios- 
TRAcUM, from the membranous skin covering the bones of qua- 
drupeds. 
EPIPHRAGM. The membranaceus or calcareous substance by 
which some species of molluscs close the aperture of the shell 
when they retire within them to hibernate. | When the animal 
wishes to come forth from his hiding place, again to 
breath the air, the edges of the Epiphragm are detached by a 
chemical process, so that it drops off. The name Hibernaculum 
has also been applied to this covering. 
EPO'NIDES. Montf. A genus of microscopic Foraminifera. 
EQUILA’TERAL. (quus, equal; Jatus,side.) Equal-sided. 
Applied to bivalve shells, when a line drawn _perpendicu- 
larly from the apex would divide the shell into two equal parts. 
Ez. Pectunculus Pilosus, fig. 134. 
E'QUIVALVE. (Aiquus, equal; valva, valve.) Applied toa 
shell when the two valves are alike in depth, width, length, &c. 
