262 A. K Veirill—Mollusca of the JSfeio England Coast. 



recorded by me as Pecten tenuicostatu$, var. aratus, shows that they 

 are in all resjiects essentially identical. In the fossil specimens the 

 ribs are much stronger and more regular than in ordinary specimens 

 of P. tenuicostattis, but not more so than in many deep-water speci- 

 mens taken in 65 to 125 fathoms, off Martha's Vineyard ; while 

 among the numerous specimens dredged by us, all gradations be- 

 tween the strongly ribbed form and those forms, common in shallow 

 water, in which the ribs are much more slender, indistinct, or almost 

 obsolete. The forms of the main shell and of the auricles are the 

 same, however, in all these varieties. The fossils, like all the recent 

 specimens, show the peculiar, tine, oblique striae or vermiculations 

 between the ribs, both on the body of the shell and on the auricles. 

 In the fossil specimens the ribs, especially those towards the ends of 

 the shell and on the auricles, are crossed by the raised lines of 

 growth in such a way as to form small, rather close, distinctly 

 arched, raised scales ; this character, which is not usually seen in the 

 smoother, shallow-water form, is found in many of the deep-water 

 specimens quite as prominently, or even more so, than in the fossil. 



There being no doubt, therefore, of the identity of the fossil and 

 recent shells, the name, CUntonius, should be adopted for the spe- 

 cies, on account of its priority, while the name, tenuicostatics, may 

 well be retained to designate the ordinary smoothish, mostly shal- 

 low-water variety, found on the New England coast. This name 

 was originally given by Dr. Mighels to very young specimens of this 

 smoothish variety, under the impression that they were a distinct 

 species, but he afterwards recognized the fact that they were only 

 the young of the common species, at that time generally known as 

 Pecten Magellanicns Lam. 



The following species should have been inserted on page 206. 

 Propilidium pertenue ? Jeffreys. 



Proc. Zool. Soc. London, for 1882, p. 6U, pi. 50, flg. 1. 

 Four or five specimens of a small limpet occurred at station 1124, 

 in 640 fathoms, in the egg-case of a species oi Jiaia, associated with 

 Choristes elegans. These agree in most respects with P. pertenue 

 Jeff., but the beak is nearer to the posterior margin, and the shell is 

 thin and opaque white, without much luster, even when living, but 

 the surface is nearly smooth, though showing slight but distinct lines 

 of growth and sometimes faint traces of microscopic radiating lines, 

 in this respect and the position of the beak resembling more P. coni- 

 pressurn Jeff. 



