212 Mr. A. Murray on a marked variety 0/ Patella vulgata. 



On comparing the two shells, however, there are other differ- 

 ences, besides its habitat and the colour of the animal, which 

 seem inconsistent with the idea of its being athletica. Its shell 

 never reaches the size of that species. It is rounder in shape. 

 It wants the china-like texture in the interior, and its colour 

 there, instead of being whitish, is yellowish cream-colour or 

 orange-brown : the exterior also is much darker. It wants the 

 thickness and solidity of athletica, or full-grown specimens of 

 vulgata ; and the substance of the shell itself, instead of being 

 dirty white, is more or less tinged with yellow and brown, — 

 although I differ from Prof. Forbes in thinking this a character 

 worthy of much reliance. Further, although the ribs have the 

 prominence and aspect of those of athletica, they are more nu- 

 merous, and want the tooth-like scales arranged in successive 

 rows, given as an essential character of the latter by Forbes and 

 Hanley. The dark colour of the interstitial spaces also is not 

 blotched, as in athletica, but uniformly continued from the base 

 to nearly the apex, which is generally orange-yellow, although 

 sometimes whitish. I may add, that the empirical character or 

 general appearance of the shell (which is a kind of testimony by 

 no means devoid of weight) speaks strongly in favour of its 

 being distinct from athletica. The two shells are so different in 

 their appearance on the rocks, that even a person wholly un- 

 acquainted with conchology could, after they had once been 

 pointed out to him, readily and correctly say to which kind every 

 new specimen that was seen belonged, — a test which was more 

 than once successfully applied by Dr. Knapp. 



I think therefore, on the above grounds, we may assume that 

 it cannot be referred to athletica. It would appear to come 

 nearer vulgata, although there are differences which almost ap- 

 pear specific. It certainly has more resemblance to some of 

 the forms of young shells of vulgata than to any other species ; 

 but this shell, although no larger than these young shells, is 

 full-grown. The animal of this shell is much darker than that 

 of vulgata, which is usually a more or less deep slate-colour or 

 dirty white. The shell too is almost invariably depressed, and 

 never assumes the large, high, conical form of the full-grown 

 vulgata. It has the rich brown markings of athletica on the 

 exterior, and a well-defined dark-brown line running up the in- 

 terstitial spaces. The ribs are particularly prominent, and it 

 has (though in a less degree) the jagged and denticulated mar- 

 gin characteristic of athletica. The colour of the tops of the 

 ribs both in athletica and the present shell is white, particularly 

 marked when the shell is cleaned, which is not the case with 

 vulgata. In the foregoing differences we see that it borrows 

 some of its characters from athletica, and some from vulgata ; 



