CYMBA. 131 



shelly and spiral. Two other genera of land shells are provided 

 with opercula, and consequently might be confounded with this 

 genus. In Helicina, the operculum is concentric and the peri- 

 treme is not continuous ; while in the small genus hitherto almost 

 unknown of Pupina, the peritreme is not continuous and there is 

 a glassy enamel over the whole of the external surface. In the 

 plates we have represented, C, ferrugineum, fig. 303 ; C. in vol- 

 vulus, fig. 304. 



CYCLOTUS. Guild. A sub-genus of Cyclostoma, consisting of 

 those species which are discoidal, as C. Planorbulum. Fig. 



CYLINDER. Montf. Conus textile, Auct. (fig. 461) and other 

 species having a cylindrical form. 



CYLINDRELLA. Sw. A genus of the family « Ovulinse," Sw. 

 composed of cylindrical species of Ovulum ? The wood-cut 

 illustrating this genus has the appearance of a Bulla. 



CYLINDRICAL. (KvXivSpog, a cylinder.) This like other ma- 

 thematical terms is used with great latitude by Conchologists, and 

 applied to any shell the sides of which are nearly parallel, with 

 the extremities either rounded, flat, or conical. Ex. Oliva, fig. 457. 



CYLLENE. Gray. Fam. Purpurifera, Lam. — Descr. Oval, thick, 

 with a short acute spire ; an oval aperture terminating anteriorly 

 in a slight emargination, posteriorly in a short canal ; a fold at 

 the lower end of the body whorl ; outer lip thick, striated within ; 

 angle of the whorls tuberculated. — Obs. This genus of small 

 marine sheUs resembles Voluta in general character, but differs 

 in having a smooth columella without folds. Recent, Pacific 

 Ocean 5 Fosil, London clay. Fig. 425. 



CYMBA. Brod. (Cymba, a boat or skiff.) Fam. Columellaria, 

 Lam. — Descr. Smooth, ventricose, with a very short, mammillated, 

 rude spire ; and a very large, wide aperture, terminated anteriorly 

 in a deep emargination ; posteriorly in a flat ledge, which sepa- 

 rates the outer lip from the body whorl ; columella with three or 

 four oblique, laminar, projecting folds, terminating in a point ; 

 outer lip thin, with its edge sharp; epidermis smooth, brown, 

 covered partly or entirely by the glassy enamel, which, com- 

 ic 2 



