CHAMA. 105 



inner lip thin. C. sulcata, Sw* fig. 38. p. 204." (Sw. Lard. Cyclop. 

 Make. p. 342.) 



CEEITHIDEA. Swainson. Part of Potamis, sp. decoUatus, 

 with rounded whorls, and spread outer lip sinuous at the base. 



CEEITHIOPSIS. Porbes and Hanley, 1851. A genus of shells 

 distinguished from Cerithium on purely anatomical grounds. 

 Ex. C. tuberculare. British Moll. PL xci. figs. 7, 8. p. 365. 



CEEITHIUM. Adanson, 1757. Fmn. Canalifera, Lam. En- 

 tomostomata, Bl. — Desc, Elongated, ribbed, tuberculated, or 

 rarely smooth, with a lengthened, turrited, pointed, pyramidal 

 spire, consisting of numerous whorls ; aperture sub-quadrate, 

 terminated anteriorly by a tortuous canal ; outer lip thickened, 

 sometimes reflected, expanded ; inner lip thickened posteriorly ; 

 operculum horny, spiral, with numerous whorls. — Obs. The 

 fresh- water shells described as Cerithia by Lamarck, are separated 

 under the name Potamis, and maybe known by the thick, horny 

 epidermis. Triphora, Desh. has the canal closed, except at the 

 extremities. Cerithium Telescopium, does not appear to present 



^ the same characters as the other Cerithia, and has been separated 

 by some writers under the generic name Telescopium. Cerithium 

 Aluco, fig. 372. Mediterranean, East and "West Indies, Coasts 

 of the Pacific, Gallapagos, Australia, &c. Some small species are 

 British. Possils are numerous in the tertiary beds. PL xyii. 

 fig. 372. 



CEHYICOBEANCHIATA. Bl. The second order of Parace- 

 phalophora Hermaphrodita, Bl. containing symmetrical pateUi- 

 form shells, divided into the families Retifera and Branchifera. 



CETOCIS. Montf. Fam. Orthocerata, Lam. and BL Placed by 

 De Blainville in his section of Belemnites, characterized as having 

 small folds at the apex. Ex. B. Penicillatus. 



CETOPIRUS. Ranz. Coeonula Bal^kakis, Auct. PL i. fig. 16. 



CH^ISTA. G-ray. Eistulana, Lamarck. 



CHAMA. Linnaeus. Fam. Chamacea, Lam. and Bl. — Descr. 

 In^quivalve, irregular, thick, foliaceous, attached by the umbo 

 of the lower and larger valve. External ligament placed in a 

 groove, following the curve of the umbones. Umbones spiral. 



