PATELLA. 427 



terior, which is rarely at all nacreous, is either whitish, or 

 of a pure orange-yellow, with which hue the spatula, iu 

 the more typical specimens, is more or less stained or 

 bordered : the margin of the shell is often articulated with 

 brown and white, and is greatly jagged or dentated, owing 

 to the projection of the external costellse. These last 

 are extremely numerous, more or less sharply angulated, 

 prominent considering their narrowness, and regularly, 

 crowdedly, and finely muricated ; they are sometimes 

 simple, and of equal width to each other (in some indi- 

 viduals, chiefly foreign, there are as many as from 100 

 to 150, and all so closely set that the interstitial spaces 

 are no broader than themselves) ; sometimes arranged in 

 triplets, of which the central riblet is rather the largest. 

 The vertex, as in vulgata, is rather blunt, and is less 

 subcentral in the more elongated than in the broader 

 examples. 



None of our known British specimens are quite so large 

 as certain of the preceding species, but we possess some 

 (possibly exotic ones) that measure nearly two inches in 

 length and about an inch and a half in width, which is 

 twice the general size of those taken upon our coast. 



Our belief in the propriety of keeping this Limpet dis- 

 tinct from vulgata is importantly sujjported by observations 

 communicated to us by Mr. Clark, who, when not aware 

 that the form had been regarded and named as a separate 

 species, decided for himself that it was such, after an 

 examination of the shells of several hundreds of both and 

 a careful comparison of their animals. We have recently, 

 with his notes in hand, carefully compared the soft parts of 

 each species alive, and can fully verify the following ac- 

 count. Of athletica he remarks, that " the animal difters 

 specifically from vulgata ; its colour is invariably much 



