152 EEYILIl. 



EPIPHEAGM. The membranaceous or calcareous substance by 

 wbicb some species of molluscs close the aperture of the shell, 

 when they retire within it to hibernate. "When the animal 

 wishes to come forth from his hiding-place, again to breathe the 

 air, the edges of the Epiphragm are detached by a chemical pro- 

 cess, so that it drops off. The name Hibernaculum has also been 

 given to this covering. It must not be confounded with the 

 operculum, which is a permanent portion of the shell, and is 

 used as a door, fitted to the foot of the animal and moved at will 

 to pen or close the aperture of the shell, whereas the Epiphragm 

 is produced for the occasion from a mucous secretion of the ani- 

 mal and dissolved at the edges when no longer wanted, when it 

 drops off. 



EPISTTLA. Swainson, 1840. A subgenus of the genus Heltx. 

 E. conical. Sw. Helix Epistylium, fig. 281. 



EPONIDES. Montf. A genus of microscopic Eoraminifera. 



EQUILATEEAL. {Mquus, efiuaX ; latus,^\dLQ) Equal-sided. A 

 term applied to bivalve shells, when a line drawn down perpen- 



• dicularly from the apex would divide the shell into two equal 

 parts. Ex. Pectunculus pilosus, fig. 134. 



EQUIVALVE. {Mquus, equal ; valva, a valve.) A term applied 

 to a bivalve shell when the valves are equal to each other in 

 dimensions. 



EEATO. Eisso, 1826. Fam. Convolute, Lam.— Descr. Ovate, 

 more or less angulated, smooth or granulated, with a dorsal 

 scar, spire short, aperture large, angulated, emarginated ; 

 columella slightly crenated ; outer lip reflected, denticulated on 

 the inner edge. Suture of the whorls covered with enamel, — 

 Obs. This genus of shells resembles Marginella in form, but has 

 no folds on the columella. Having a scar or groove do^Ti the 

 back it may be considered intermediate between Marginella and 

 Cyprsea. In the Author's Conchological Illustrations, seven 

 species are enumerated and figured. E. Maugerise. PI. xxi. 

 fig. 454. 



EEUCA. Sw. A subgenus of Clausilia. Sw. Malac. p. 334, 



EEVILIA. Turton, 1822. A genus described as " oval, equi- 



