EFFUSE. (_effundo_, to pour out.) The aperture of an univalve shell is said to be effuse when there is a notch in the margin which would suffer a liquid to escape, and thus prevent it being filled to the brim. EGEON. Montf. A genus of microscopic Foraminifera. EGERIA. Lea. (Contrib. to Geol. p. 49, pl. 1.) A genus of fossil bivalves, described as very variable in form, with or without lateral teeth, sometimes a crenated margin, &c. The only certain characters appear to be that they have two diverging cardinal teeth in each valve, one of which is bifid; and an external ligament. Lea states that the Egeriæ should be placed between the Sanguinolariæ and the Psammobiæ, which two latter genera have been united by Sowerby. Fig. 103, E. Triangulata, from the tertiary formation of Alabama. ELENCHUS. Humph. A genus composed of TROCHUS Iris, Auct. and other similarly formed species. It is the same as CANTHARIDUS of Montfort. ELEPHANT'S TUSK. The common name given by dealers to shells of the genus Dentalium. _Ex._ D. octogonum, fig. 2. ELEVATED. A term which is applied by some conchological writers to the spire of an univalve shell when it consists of numerous whorls drawn out into a telescopic form. Other authors use the term _elongated_, or the more simple one '_long_,' to express the degree of elevation. ELISMA. Leach. A sub-genus of Bulinus. B. acutus, Auct. Gray, Turton, p. 185. ELLIPSOLITHES. Montf. ([Greek: Elleipsis], _ellipsis_, oval; [Greek: lithos,] _lithos_, stone.) A genus composed of Ammonites, which instead of being regularly orbicular, take an elliptical or oval form. This character appears to be accidental, as some individuals of the same species, both of Nautilus and Ammonites, are round, while others are compressed into an oval form. ELLIPSOSTOMATA. Bl. ([Greek: Elleipsis], _ellipsis_, oval; [Greek: stôma], _mouth_.) The third family of the class Asiphonibranchiata, Bl. The shells of this family are described as of various forms, generally smooth; the aperture longitudinally or transversely oval, completely closed by a horny or shelly operculum. This family contains the genera Rissoa, Phasianella, Ampullaria, Helicina, and Pleuroceras. ELLIPTICAL. ([Greek: Elleipsis], _ellipsis_.) Oval. Applied to any shell or part of a shell, having that form. ELMINEUS. Leach. _Order_, Sessile Cirripedes, Lam.--_Descr._ Four unequal valves, arranged circularly side by side, forming a quadrate cone; aperture large, sub-quadrate, irregular; operculum composed of four valves, in pairs.--_Obs._ This genus differs from Conia in the structure of the shell, the latter being porous. Fig. 22, Elmineus Leachii. ELPHIDIUM. Montf. (Conch. Syst. t. 1. p. 15.) A genus of microscopic Foraminifera.