36 MOLLUSCA FROM THE CRAG. 



recent shell that I have no doubt of its identity. Var. #, probably B. striatum 

 Pennant, appears to be rather of an aberrant form in this species ; the outer lip is 

 similarly sinuated, but not periodically thickened, and the consequent absence of the 

 undulatory elevations upon the body of the shell gives a great apparent difference to 

 this variety. The figures above referred to are of course the extreme forms, but I 

 think they can be fairly connected by the series I possess. The proportionate 

 dimensions of the aperture, with regard to the axis of the shell, is a character by 

 no means constant. 



PURPURA,* Adanson, 1757. 

 BUCCINUM (spec.) Linn. 



Gen. Char. Shell ovate, thick, and strong; spire generally short, sometimes 

 elongated ; external surface striated, sulcated, muricated, granulated, or tuberculated ; 

 aperture ovate, somewhat dilated ; outer lip crenated, occasionally dentated within ; 

 columella usually flattened ; base subcaniculate or emarginate. Operculum corneous, 

 with a lateral nucleus. 



Shells of this genus are generally very thick and strong, and may be distinguished 

 from Nassa or Buccinum by a peculiar flatness upon the columella, while they resemble 

 those genera in many other characters. The canal is short, straight, and not re- 

 flected ; but the animal is said to present several constant characters, by which it 

 may be considered as distinct. 



It is not yet known as an Eocene fossil, though M. Deshayes speaks of it as from 

 some beds of the Oolitic period. 



1. PURPURA LAPILLUS. Linn. Tab. IV, fig. 6, a h. 



PURPURA LAPILLUS, VET. fl, CEISPATA. S. Wood. t. 4, fig. 6, . 



6, BREVIS fig. 6, b. 



C, ELONGATA fig. 6, C. 



d, VULGARIS fig. 6, d. 



, ANGULATA - fig. 6, e.f 



f, CARINATA fig. 6,/. 



g. IMBRICATA - fig. 6, g. 

 h, INCRASSATA - fig. 6, h. 



i, COMPRESSA, t. 19, fig. 12, a, b. 

 BUCCINUM LAPILLUS. Linn. Syst. Nat. p. 1202, 1766. 

 TRITONIUM LAPILLUS. Mull. Zool. Dan. Prod. 244, 1776. 

 PURPURA LAPILLUS. Lam. An. sans Vert. torn, vi, 1815. 

 BUCCINUM CRISPATUM. J. Sow. Min. Conch, t. 413, 1823. 



INCRASSATUM. t. 414, fig. 2. 



* Purpura, "the shell-fish from which purple is taken." The celebrated dye of the ancients is now 

 considered to have been produced from the Murex trunculus, a shell common in the Mediterranean, and not 

 from the Purpura lapillus, which is not known in that part of the world. 



f This is from the cabinet of Mr. Lyell. 



