Part 34

ENSIS. Schum. SOLEN ensis, Auct. and similar species.

ENTALIS. Defr. DENTALIUM duplicatum, Bl. PHARETRIUM, König. This genus is described as a small tube, within a larger one, the smaller extremity of the inner tube projecting beyond that of the outer one. Deshayes, who describes this genus, expresses a conviction that the soft parts of the animal must be entirely different from those of the animal of Dentalium. The genus PHARETRIUM, as described by König in his "Icones Fossilium Sectiles," is evidently identical with Entalis. It is placed by him in the family of Pteropoda, but being a fossil shell, there is some difficulty in finding its place in the system. See plates, fig. 3.

ENTELLITES. Fischer. A genus composed of species of TEREBRATULA, SPIRIFER, and PRODUCTUS, Auct. having the hinge large and the umbones short. ORTHIS? Dalman.

ENTIRE. (Integra.) Not interrupted, not emarginated. The peritrême of a univalve shell is said to be entire when not interrupted by canals or by the body whorl. Ex. Cyclostoma, fig. 304. The palleal impression is entire, when continued without interruption, or without a sinus.

ENTOMOSTOMATA. Bl. The second family of the order Siphonibranchiata, Bl. The shells of this family are described as differing but little from those contained in the family of Siphonostomata of the same author, both with regard to the soft parts, and their testaceous covering. This family partly answers to the Purpuriferæ in the system of Lamarck, and contains the genera Subula, Cerithium, Melanopsis, Planaxis, Terebra, Eburna, Buccinum, Harpa, Dolium, Cassidaria, Cassis, Ricinula, Cancellaria, Purpura, Concholepas.

EOLIDES. Montf. A genus of microscopic Foraminifera.

EPIDERMIS. ([Greek: Epi], epi, over or upon; [Greek: derma], 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 analogous to the nails and hair. Gray calls it the PERIOSTRACUM, from the membranous skin covering the bones of quadrupeds.

EPIPHRAGM. The membranaceous or calcareous substance by which 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 process, 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 open or close the aperture of the shell, whereas the Epiphragm is produced for the occasion from a mucous secretion of the animal and dissolved at the edges when no longer wanted, when it drops off.

EPISTYLA. Sw. A subgenus of the genus HELIX. E. conical. Sw. Helix Epistylium, fig. 281.

EPONIDES. Montf. A genus of microscopic Foraminifera.

EQUILATERAL. (Æquus, equal; latus, side.) Equal-sided. A term applied to bivalve shells, when a line drawn down perpendicularly from the apex would divide the shell into two equal parts. Ex. Pectunculus pilosus, fig. 134.

EQUIVALVE. (Æquus, equal; valva, a valve.) A term applied to a bivalve shell when the valves are equal to each other in dimensions.

ERATO. Risso. Fam. Convolutæ, 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 down the back it may be considered intermediate between Marginella and Cypræa. Fig. 454, E. Maugeriæ. In the Author's Conchological Illustrations, seven species are enumerated and figured.

ERUCA. Sw. A subgenus of Clausilia. Sw. Malac. p. 334.

ERVILIA. Turt. A genus described as "oval, equivalve, equilateral, closed. Hinge with a single erect tooth closing between two small diverging ones in the opposite valve: lateral teeth none. Ligament internal. E. nitens. Turt. Mya. nitens, Auct."

ERYCINA. Lam. Fam. Mactracea, Lam. Conchacea, Bl.--Descr. 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 impressions sinuated. East and West Indies and Mediterranean.--Obs. This genus is distinguished 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.

ERYTHRÆA. The ancient name for CYPRÆA.

ESCUTCHEON. The impression on the posterior dorsal margin of some bivalve shells. That on the anterior margin is named the lunule. The escutcheon is pointed out by the letter e in some of the figures of Cythereæ. Fig. 117, a. b. c.

ETHERIA. Lam. (Æther, air.) Fam. Chamacea, Lam. and Bl.--Descr. Irregular, inequivalve, inequilateral, foliaceous, pearly within, covered by an olive green epidermis without; hinge callous, undulated, destitute of teeth; ligament partly external, partly internal, passing through the hinge on a somewhat raised, callous area in the lower valve. Muscular impressions elongated, two in each valve, united by a slender palleal impression. Rivers of Africa.--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 ugliness of the exterior. In its irregular form, foliated structure, and toothless hinge, it resembles OSTREA, from which it differs in having two muscular impressions. Fig. 155, E. semilunata.

EULIMA. Risso. Fam. Scalariens, Lam.--Descr. Elongated, smooth, pyramidal; spire long, composed of numerous 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. A complete illustrated monograph of this genus of pretty shining little shells, consisting of 15 known species, is given in parts 52 and 53 of the Conchological Illustrations by the author.

EUOMPHALUS. Sow. Fam. Scalariens, Lam.--Descr. Orbicular, planorbular spire, with three or four volutions, imbricated above; smooth below; aperture of a round polygonal form; umbilicus large, penetrating to the apex of the shell.--Obs. This genus of fossils very nearly resembles Delphinula. The main difference appears to be that the whorls do not increase so rapidly in size in the former as in the latter. Fossil, in the Carboniferous Limestone. Fig. 350.

EXOGYRA. Sow. A genus of fossil bivalves, resembling Chama in shape and Ostræa in structure, having but one muscular impression in each valve. Fig. 183.

EXSERTED. Standing out, protruding.

EXTERNAL. An external shell is one which contains the animal, and is not covered by the mantle.

FASCIATED. (fascia, a band.) Banded or striped. Ex. Carocolla marginata, fig. 277.

FASCICULATED. (from fasciculum.) A little bunch of hairs or bristles against each end of each valve, characterizes some species of the genus Chiton, which are termed fasciculated species.

FASCIOLARIA. Lam. Fam. Canalifera, Lam. Siphonostomata, Bl.--Descr. Elongated, fusiform, ventricose; spire conical, consisting of few rounded or angulated whorls; aperture wide, terminating in a long straight open canal: columella lip with several oblique folds, the lower of which is larger than the rest; operculum horny, pyriform.--Obs. This genus is known from Fusus by the folds on the columella; from Turbinella, by their obliquity and the last being larger than the rest. Fig. 386, F. Trapezium. East and West Indies and Australia.

FAUNUS. Montf. MELANOPSIS, Auct.