CONCHOLEPAS. MOLLUSCA. 33 



This, although not the most beautiful, is the rarest and most valuable of the ge- 

 nus. It is readily distinguished by the spiral carina around the spire. 



H. ventricosa, Lam. Shell ventricose, with broad depressed distant 

 ribs, mucronate near the sutures, and flesh-coloured, with trans- 

 verse brown and white markings ; the interstices flesh-coloured, 

 with longitudinal reddish and white undulations; columella blotch- 

 ed with deep brown. Nearly 4 inches long. Inhabits the Indian 

 seas . Bonan. 3, fig. 185. 

 This is the most common, and at the same time the most beautiful species of the 



genus. 



Gen. 17. CONCHOLEPAS, Lam. Buccinum, Brug. 

 Shell ovate, inflated, semispiral, the apex inclined obliquely to- 

 ward the left lip ; aperture wide, longitudinal, oblique, fur- 

 nished beneath with a slight notch ; two teeth at the base of 

 the right lip ; an oblong, thin, horny operculum. 



Of this singular genus there is only one species known. 



C. Peruvianus, Lam. Three inches long. Inhabits the coasts of 

 Peru Lam. vii. 253. 



Gen. 18. MONOCEROS, Lam. Buccinum, Brug. 

 Shell ovate ; aperture longitudinal, emarginate at the base ; a 

 conical tooth at the base of the right lip. 



These shells are only distinguishable from the Purpurae by the more or less pro- 

 minent tooth at die base of the right lip. They inhabit the coasts of America. 



M. imbricatum, Lam. Shell ovate, ventricose, roughish, gray or 

 grayish-red, with crowded imbricated transverse ribs; whorls 

 convex ; the outer lip crenulate. 2J inches long. Inhabits the 

 Straits of Magellan Favanne, Conch, pi. 27, fig. D. 1. 



Gen. 19- PURPURA, Lam. Buccinum, Lin. 

 Shell ovate, smooth, tubercular or angular ; aperture dilated, 

 emarginate at the base, with an oblique subcanaliculate sinus ; 

 columella flattened, ending below in a point. 



It is chiefly in the Mollusca of this genus that the colouring matter of which the 

 ancients formed their beautiful purple is found : 



Tyrioque ardebat Murice lana. 



The colouring matter occurs in a vesicular reservoir near the stomach. It is no long- 

 er used, however, the discovery of cochineal having furnished an abundant supply 

 of equally beautiful and more easily procured colour. The Furpura occur in all 

 seas, and are littoral. 



P. Persica, Lam. Shell ovate, transversely sulcate, roughish, dark 

 brown, the ridges spotted with white ; spire short ; aperture pa- 

 tulous ; columella yellow, longitudinally excavated in the mid- 

 dle ; outer lip sulcate on the inner margin, and blackish white 

 within, marked with yellow lines. 3 inches long. Inhabits the 

 Indian seas Lister, pi. 987, fig- 46. 



P. patula, Lam. Shell ovate, transversely sulcate, tubercular, reddish- 

 black ; spire shortish ; aperture patulous ; columella reddish-yel- 

 low ; outer lip white within. 3 inches long. Inhabits the Me- 

 diterranean sea.Bonan. 3. fig. 368. 



This is supposed to be the species from which the Tyrian purple was obtained. 

 VOL. II. C 



