154 CONCHOLOGY. 



R. digitata. The digitated Ricinula. 

 Species canaliculated ; two long palmated digits at the 

 side of the aperture. 



4. Purpura. Fifty species. 



This genus has its name from the purple liquid produced 

 by the animal, from which the ancients extracted the Tyrian 

 purple die. This is the last genus that presents the ap- 

 pearance of a canal at the base of the aperture, and therefore 

 rightly precedes the remaining genera of this family, all of 

 which are without a canal. 



Shell oval, thick, generally tuberculated ; spire short ; the 

 last whorl much greater than all the others united ; aperture 

 oval, greatly dilated, terminated anteriorly by a canal short, 

 oblique, and notched at the extremity ; the columellar edge 

 almost straight, covered with a callosity pointed anteriorly ; 

 operculum horny, flat, almost semicircular, with transverse 

 striae slightly marked ; the summit behind. 



Purpura Persica. Purpura sacellum. 



P. Rudolphi. P. squamosa. 



P. patula. P. rugosa. 



P. collumellaris. P. textilosa. 



P. succincta. P. sertum. 



P. consul. P. Francolinus. 



P. armigera. P. limbosa. 



P. bitubercularis. P. ligata. 



P. hippocastanum. P. cruentata. 



P. undata, P. lapillus. 



P. hasmastoma. P. imbricata. 



P. manicella. P. lagenaria. 



P. bufo. P. cateracta. 



P. callosa. P. bicostalis. 



P. neritoides. P. plicata. 



P. planospira. P. fiscella. 



P. callifera. P. thiarella. 



P. coronata. P. rustica. 



