484 



HALIOTID^. 



The ear-shells constitute a very natural passage from the 

 Patelliform Mollusks to the Trochus tribe, combining in 

 both animal and shell many of the features of the latter 

 family with some of the peculiarities of the FissureWdce. 

 Milne Edwards * has described some remarkable arrange- 

 ments of the circulatory system common to Haliotis and 

 Patella, whilst the dental system of the former genus 

 strikingly reminds us of Trochus, as do the pedunculated 

 eyes, lobed head- veil, and cirrhated side-lobes. There are 

 two branchial plumes. The shell is greatly expanded and 

 furnished with a short and small spire ; in most cases 

 it is either notched or perforated at intervals, in this re- 

 spect approaching Emargimda and its allies. The typical 

 genus Haliotis, though one of great extent in tropical and 

 southern regions, where it includes numerous and gigantic 

 species often of exquisite beauty, is included in the British 

 Fauna rather by courtesy than by strict right, seeing that 

 its range does not extend beyond the Channel Islands. 



PIALIOTIS. LiNNiEus. 



Shell ear- shaped, depressed, externally smooth or undu- 

 lated or striated, internally nacreous ; spire very short, and 

 placed as if laterally ; mouth very large, broader than 



* Ann. des Sc. Nat., Series 3, vol. viii. p. 'tf. 



