92 CALLOSITY. 



tion with regard to the operculum. The only difference between 

 the genera Trochus and Turbo, as at present established, de- 

 pends upon the calcareous or shelly, and the corneous or horny, 

 texture of the operculum. 



CALCEOLA. Fam. E-udistes, Lam. and 'Si.—Bescr. Equilateral, 

 inequivalve, triangular ; umbones separated by a large triangular 

 disc in the lower valve; cardinal margin straight, linear, dentated, 

 lower valve large, deep ; upper valve flat, semi-orbicular, forming 

 a kind of operculum to the lower. — Obs. This singular shell, 

 known only in a fossil state, in the Palaeozoic beds, is placed by 

 Linngeus in the genus Anonia. Lamarck places it among his 

 Eudistes, but Mr. Sowerby, in his genera of shells, states that 

 it should be added to the family of Brachiopoda, C. Sandalina, 

 PL xi. fig. 194, 195. 



CALANTICA. Gray. Part of Scalpellum. 



CALLIA. Grray, 1840 ? A genus described as having a pecu- 

 liarly polished shell like Pupiaa, but wanting the notch, PL xxv. 

 fig. 528. 



CALLIPAEA. Swainson. Voltjta bullata ; Sowerby's Thesaurus 

 Conchyliorum, PL liii. fig. 88. 



CALLISOSTOMA. Sw. A genus of shells separated from Teo- 

 CHTJS, and thus described: " Imperforate ; spire elevated, acute ; 

 aperture broader than high, transversely ovate, hardly sinuated 

 at the base, and slightly oblique ; shell always smooth, and often 

 polished." C. zixyphina is mentioned as an example. 



CALLISCAPHA. Gray ? Ieidina Nilotica, Sow. Zool. Journ. 

 1. pL 2. Separated from Iridina on account of the hinge margin 

 being smooth- 



CALLITHEA. Sw. A sub-genus of Mitrae, consisting of those 

 species, which like M. sanguisuga, have the " spire and aperture 

 of nearly equal length : internal channel nearly obsolete ; shell 

 with longitudinal linear ribs, crossed by transverse striae and 

 bands ; base contracted." Svainson, MaUac. Lard. Cyclop. 



CALLOCHITON. Gray, 1847. Chiton Isevis, &c. 



CALLOSITY. A term used in general zoology to express those 

 hard homy tumidities formed in the skin of some animals (such 



