EUOMPHALUS. 43 
ERA’TO. Risso. Fam. Convolute,Lam. Descr. Ovate, more 
or less angulated, smooth or granulated; with a dorsal scar, 
short spire, and large, angulated, emarginated aperture. Colu- 
mella slightly crenated; outer lip reflected, denticulated on the 
inner edge. Suture of the whorls covered with enamel. Obs. 
This genus of small shells resembles Marginella, but has no folds 
on the columella. Having a scar or groove down the back, it is 
considered intermediate between Marginella and Cyprea. 
Fig. 454, E. Maugeriz. 
ERVILIA. Turt. E. Nitens. Mya Nitens. Montf. 
ERYCINA. Lam. Fam. Mactracea, Lam. Conchacea, Bl. Ovate 
or triangular, transverse, equivalve, inequilateral, smooth; 
hinge with a ligamentary pit, two diverging cardinal and two 
lateral teeth in each valve; muscular impressions two in each 
valve ; palleal impression sinuated. Obs. This genus is distin- 
guished from Mactra and Lutraria, by the cardinal teeth being 
placed one on each side of the ligamentiferous pit ; whereas in 
the last named genera they are both placed on the anterior side. 
Fig. 86, E. Plebeja. 
~ERYTHRAVA. The ancient name for Cyprma. 
ESCUT’CHEON. The impression on the posterior dorsal mar- 
gin of some bivalve shells. That on the anterior dorsal margin 
is called the lunule. ‘The Escutcheon is indicated by the letter e 
in some of the Cytheree, fig. 117, a.b. c. 
ETHERIA. Lam. (Aither, air.) Fam. Camacea, Lam. and 
Bl. Deser. Irregular, inequivalve, inequilateral, foliaceous, 
pearly within, covered by an olive green epidermis without ; 
hinge callous, undulated, destitute of teeth; ligament partly ex- 
ternal, partly internal; passing through the hinge on asomewhat 
raised, callous area in the lower valve. Muscular impressions 
elongated, two in each valve, united by a slender palleal im- 
pression. Obs. The irregular, unequal, air-bubbles of the inner 
surface, whence this genus derives its name, are very brilliant 
in some species, and atone in some measure for the rugged ugli- 
ness of the exterior. In its irregular form, foliated structure, and 
toothless hinge, it resembles Ostrma, from which it differs in 
having two muscular impressions. Fig. 155, E. semilunata. 
EU’LIMA. - ? Fam. Scalariens, Lam. Descr. Elongated, 
smooth, pyramidal; spire long, composed of numerous angu- 
lated whorls; apex acute, slightly tortuous; aperture oval, 
rounded anteriorly, acute at the posterior union with the body 
whorl; outer lip slightly thickened; columella smooth. Fig. 
347, E. labiosa. Fig. 348, E. splendidula. 
EUOM’PHALUS. Sow. Fam. Scalariens, Lam. Deser. Orbi- 
cular, conical; spire short, with three or four volutions, imbri- 
cated above. smooth below; aperture of a round polygonal 
form; umbilicus large, penetrating to the apex of the shell. Obs. 
