MO CTTHEREA. 



species are found in the tertiary deposits. Cyprina may be 

 known from Yenus by tbe remote lateral tooth and the thick 

 epidermis. C. yulgaris, PL v. fig. 116. 



CYEENA. Lamarck, 1818. Fam. Fluviatile Conchacese, Lam. 

 Conchacea, Bl. — Bescr. Suborbicidar, equivalve, inequilateral, 

 ventricose, corroded at the umbones, thick, covered with a thick 

 epidermis ; hinge with three cardinal and two remote lateral 

 teeth in each valve. Muscular impressions two in each valve ; 

 paUeal impression not siauated. — Obs. This genus is distin- 

 guished from Venus, Cytherea and Cyprina, by having two 

 remote lateral teeth ; and from Cyelas by the thickness of the 

 shell. This genus is mostly fluviatile ; the recent species are 

 tropical, and the fossU are found in the newest formations. C. 

 fuscata. PI. V. fig. 113. 



CTEENELLA. Desh. See Cyeenoida. 



CYEENOIDA. Joannis, 1835. Cteenella, Desh. Fam. Con- 

 ques Eluviatiles, Lam. — Bescr. Equivalve, subequilateral, ventri- 

 cose, thin, covered with a reddish brown epidermis, corroded at 

 the umbones, with a slight posterior fold. Hinge thin, with 

 three diverging cardinal teeth in each valve, and a very slight 

 posterior fold in the right valve. Ligament not very tumid. — 

 Obs. This fresh-water shell differs from Cyelas and Cyrena in 

 the lateral teeth, and from the latter in the thinness of the shell. 

 PL v. fig. 114. 



CYETIA. Dalman. (Kvproc, curtos, gibbose.) Fam. Brachio- 

 poda, Lam. — Bescr. " Hinge rectilinear ; with the back elevated 

 into a semicone or half-pyramid, the cardinal side perpendicularly 

 plane." — Obs. This genus of fossil Brachiopoda forms part of 

 the genus Spirifer, Sow. C. exporrecta, (Anomites exporrecta, 

 Nonnull.) PL xi. fig. 204, 



CYTHAEA. Schum. 1817. CanceUaria Cytharella. Lamaeck. 



CYTHEEEA. Lam. Fam. " Conques MarLaes," Lam.— Descr. 

 Equivalve, inaequilateral, oval, lenticular, or sub -trigonal ; hinge 

 with two or more short, diverging cardinal teeth, and one an- 

 terior approximate lateral tooth in each valve. — Obs. The Cy- 

 therese are distinguished from the Veneres by the lateral tooth. 



