116 



HALIOTIS. 



A. Perforate. (Plate XXI. %. 1.) 



B. Imperforate, (fig. 2.) 



Shell ear-shaped_, open; spire lateral, and nearly 

 hidden ; disk, in the first division, longitudinally 

 perforated with pores. 



The perforations have been considered as essen- 

 tial to the generic character of Haliotis : but still, 

 with some inconsistency, more than one imperfo- 

 rated species have found admittance ; while others, 

 which in most respects are intimately allied to the 

 genus, have for the same reason been excluded. 

 So precisely similar is the entire specimen figured 

 in our plate to the penetrated one, that no reason- 

 able doubt can exist of their belonging to the same 

 geims. The situation of the spire, the general 

 outline, the involution of the margin, the obvious 

 mode of increment, the internal and external su- 

 perficies of the shell, — all point out the necessity 

 of a distinct division to comprehend such shells as 



