Part 29

CORONULA. (Corona, a crown, dim.) Order, Sessile Cirripedes, Lam. Fam. Balanidea, Bl.--Descr. Six radiated valves, joined side by side in a circle, forming a depressed cone; internal structure of the valves, porous or chambered; thickened at the base; operculum consisting of four valves in pairs; imbedded horizontally in a cartilaginous substance.--Obs. The shells composing this genus are found partly imbedded in the skin of whales, and the shells of tortoises, and are therefore destitute of the shelly foundation on which the Balani and other Coronular Multivalves are supported. C. Testudinaria, (CHELONOBIA, Leach,) fig. 15. C. Balænarum, (CETOPIRUS, Ranz.) fig. 16. C. Diadema, (DIADEMA, Ranz.) fig. 17.

CORONULAR MULTIVALVES are those which have their parietal valves joined together side by side in a circle, surrounding the body of the animal, so as to form a sort of coronet. This is the characteristic of the Sessile Cirripedes of Lamarck's system, the Balanidea of De Blainville.

CORRODED. (Corrodo, eat away, consume.) The umbones, apices, and other thick parts of shells, are frequently worn away or consumed by the action of the element in which they exist. As the thickest parts of some shells are the most subject to this operation, it appears to the author to arise from the outer surface of the shell, being less under the influence of the animal juices than the other parts; and therefore, more exposed to the influence of the surrounding element. This, however, is not the case with respect to the Nayades and other fresh-water shells; with these, corrosion does not take place until after the thick epidermis which covers them, becomes wounded by some means or other, and then the animal thickens its shell within as fast as it is corroded without.

CORTALUS. Montf. (Conch. Syst. 1. 115.) A genus of microscopic Foraminifera, placed by De Blainville in a division of the genus Rotalites.

COSTATED. Ribbed, as Cardium Angulatum, fig. 123.

COSTELLARIA. A sub-genus of the genus Tiara, Sw. (Mitra.) C. rigida. Swainson, Zool. Ill. 1st series, pl. 29.

COWRY. A common name for shells of the genus Cypræa.

CRANIA. (Cranium, a skull.) Fam. Rudistes, Lam. Order, Pallio-branchiata, Bl.--Descr. Inequivalve, equilateral, irregular, sub-quadrate; upper valve patelliform, conical, with the umbo near the centre; lower valve attached by its outer surface; muscular impressions, 4 in each valve; two large, posterior, distant; two small, near to each other, central. No hinge teeth; no ligament.--Obs. This genus properly belongs to the Brachiopoda, Lam. It differs from Orbicula in the mode of attachment, which in the latter, is by a byssus passing through the lower valve, and not by the valve itself. Hipponyx has only two muscular impressions in each valve. The name of this genus is derived from the inner surface of the attached valve, which presents a remarkable resemblance to the facial portion of a human skull. This appearance is caused by the situation and elevated edges of the muscular impressions. Fig. 197. Coasts of Britain and Mediterranean.

CRASSATED. (Crassus, thick.) Used to express a thickness in the substance of a shell. Ex. Glycimeris, fig. 67.

CRASSATELLA. Lam. (Crassus, thick.) Fam. Mactracea, Lam. Conchacea, Bl.--Descr. Equivalve, inequilateral, close, thick, rounded anteriorly, rostrated posteriorly, with denticulated margins, smooth, or ribbed transversely; hinge with a triangular pit containing the cartilage, two anterior cardinal teeth, and a posterior depression in one valve; one anterior tooth and a slight anterior marginal elevation, and a posterior elevation in the other valve. Muscular impressions distant, strongly marked. Palleal impression not sinuated.--Obs. The few recent species known are marine, several being brought from the coasts of New Holland. Fossil species are found in Calcaire-grossier and London clay. The Crassatella are known from the Veneres, &c., by the ligamentary pit in the hinge, and from Lutraria and Mactra by the thickness and closeness of the shell. Fig. 84, C. rostrata.

CRASSINA. Lam. ASTARTE, Sow.

CRASSIPEDES. Lam. (Crassus, thick; pes, foot.) The first section of the order Conchifera Dimyaria, Lam. In this section the foot of the animal is thick, and the shell gapes considerably. It is divided into the families Tubicolæ, Pholadidæ, Solenidæ, and Myaria. Fig. 44 to 76.

CRASSISPIRA. Sw. A genus separated from COLUMBELLA, Auct. for which Mr. Swainson quotes "Pleurotoma Bottæ, Auct." Crassispira fasciata, Sw. Lardn. Cyclop. Malac. p. 313.

CRENATED. (Crena, a notch.) Applied to small notches, not sufficiently raised or defined, to be compared to teeth. Ex. The hinge of Iridina, fig. 150.

CRENATULA. Lam. Fam. Malleacea, Lam. Margaritacea, Bl.--Descr. Compressed, foliated, irregular, sub-equivalve, inequilateral, oblique; umbones terminal; hinge linear, nearly straight, with a series of excavations, containing the cartilage, while the intervening ridges are covered with the ligament, properly so called. Muscular impression oblong, indistinct.--Obs. This genus is known from Perna by the hinge, which in the latter is composed of a series of regular, straight, ligamentary grooves placed across it. In Crenatula also there is no passage for the byssus, as in Perna. C. Mytiloides, fig. 168. Coasts of the Red Sea.

CRENULATED. Finely crenated or notched.

CREPIDULA. Lam. (Crepidula, a little slipper.) Fam. Calyptracea, Lam. and Bl.--Descr. Oval, irregular, patelliform; apex lateral, incurved, or sub-spiral; external surface convex, smooth, ribbed, waved, or covered with spines; interior concave, smooth, with a flattish septum reaching nearly half across the cavity; epidermis light brown.--Obs. The difference between this genus and Calyptræa is that in the latter, the septum is more free from the sides of the shell, so that, instead of forming a regular plate, covering half the aperture, it assumes a variety of shapes, and in some is cup-shaped, in others forked, and in some forms a little angular shelf. Indeed, the variations are so numerous that I think it would be better to throw the two genera into one, and then divide them into smaller groups. Some species of Calyptræa are farther removed from each other with respect to the characters of the septum and general form of the shell, than they are from the Crepidulæ. Fig. 239. Mediterranean, North and South America, East and West Indies, New South Wales, &c.

CREPIDULINA. Bl. CRISTELLARIA, Lam. Microscopic.

CRESEIS. Ranz. Order, Pteropoda, Lam.--Descr. Thin, fragile, transparent, pyramidal, pointed; with a dorsal ridge produced into a point at the edge of the aperture.--Obs. The species found in the Mediterranean is named C. Spinifera (fig. 222), from its resemblance to a thorn.

CREUSIA. Leach. (Creux, se. Fr. a cavity.) Fam. Balanidea, Bl. Order, Sessile Cirripedes, Lam.--Descr. A depressed cone, consisting of four valves, supported upon, and jointed to, a cup-shaped cavity formed in the Madrepores, in which it resides. Aperture quadrilateral, closed by an operculum of four valves.--Obs. This genus is distinguished from Pyrgoma, which is supported on the edge of a similar cup-shaped cavity, by the paries being composed of four valves, whereas in Pyrgoma, it consists of a single piece. Fig. 28, C. Gregaria. East Indies.

CRICOSTOMATA. Bl. The second family of Asiphonibranchiata, Bl. It is thus described: "shell equally (with the animal) variable in general form, but of which the aperture, always nearly round, is completely closed by the shelly or horny operculum; whorls few, and apex sublateral." This family agrees in some measure with the family Turbinacea of Lamarck, and with the genus Turbo in the system of Linnæus. It contains the genera Pleurotomaria, Delphinula, Turritella, Proto, Scalaria, Vermetus, Siliquaria, Magilus, Valvata, Cyclostoma, and Paludina.

CRIOCERATITES. A genus composed of species of Ammonites, with disconnected whorls. C. Duvallii, fig. 482.

CRIOPUS. Poli. CRANIA, Auct.

CRISTACEA. Lam. The third family of Polythalamous Cephalopoda, Lam. This family is described as including shells of the following characters:--"Multilocular, flattened, nearly reniform; the chambers gradually increasing in length, as they approach the outer arched margin, and appearing to revolve round an eccentric, more or less marginal axis. The Cristacea contain the genera Renulina, Cristellaria, and Orbiculina."

CRISTACEA. Bl. The third family of Polythalamia, Bl. containing the genera Crepidulina, (Cristellaria, Lam.) Oreas and Linthuris.

CRISTARIA. Schum. DIPSAS Plicatus, Leach. ANODON tuberculatus, Fer.

CRISTELLARIA. Lam. CREPIDULINA, Bl. Fam. Cristacea, Lam. and Bl.--Descr. Semidiscoidal, chambered; whorls contiguous, enlarging progressively; spire eccentric, sublateral; septa imperforate. Microscopic.

CRYPTA. Humph. CREPIDULA, Lam.