262 A. EF. Verrill—Mollusca of the New England Coast. 
recorded by me as Pecten tenuicostatus, var. aratus, shows that they 
are in all respects essentially identical. In the fossil specimens the 
ribs are much stronger and more regular than in ordinary specimens 
of P. tenuicostatus, 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, fine, oblique strie 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, Clintonius, should be adopted for the spe- 
cles, on account of its priority, while the name, tenutcostatus, 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 Magellanicus Lam. i 
The following species should have been inserted on page 206. 
Propilidium pertenue ? Jeffreys. 
Proe. Zool. Soc. London, for 1882, p. 674, pl. 50, fig. 7. 
Four or five specimens of a small limpet occurred at station 1124, 
in 640 fathoms, in the egg-case of a species of Rata, 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. com- - 
pressum J eff. 
