276 OSTREAD^i. 



The shell is distributed all round the British coasts, in 

 some places very abundantly, in others it is comparatively 

 scarce, but scarcely any where gregarious. In Zetland it 

 appears to be rare, and is on the whole more common 

 in the south than in the north. It ranges from three to 

 thirty-five fathoms, but is most plentiful in from seven 

 to fifteen. It ranges throughout the European seas and 

 is yet found rarely in the fossil state, in Pleistocene beds. 



P. niveus, Macgillivray. 



Free, echinated, almost always white ; with from forty to fifty 

 distinct and elevated ribs ; ears unequal. 



Plate L. fig. 2, and (Animal) Plate S. fig. 3. 



Pectenniveus, Macgilliv. Edinburgh Nat. and Phil. Journal vol. xiii. (1825), p. 

 166, pi. 3, f. 1. — Fleming, Brit. Animals, p. 384. — Brit. Marine 

 Conch, p. 250.— Brown, Must. Conch. G. B. p. 74, pi. 24, 

 f. 16.— Sowerbv, Thesaur. Conch, vol. i. p. 77, pi. 19, £ 223, 

 224. 



The general features of this shell are so very nearly 

 identical with those of the preceding species, that it is 

 only necessary to specify those details in which it differs. 

 Of these, the most immediately perceptible is the much 

 greater number of the ribs, which range from about forty to 

 upwards of fifty, are narrower and more closely disposed, 

 and echinated by much smaller scales, whose fragility is 

 such that they are partially abraded on almost every spe- 

 cimen, and which, upon the young, are, for the most part, 

 only visible at the extreme sides. The general shape is ra- 

 ther more orbicular than in varius, and the auricles are not 

 so disproportionate, the area of the larger one (which is by 

 no means of such amplitude as in the previous species) not 

 exceeding twice that of the other, and its upper or cardinal 



