A. E. Verrill on the Mollusca of Europe and N. America. 7 
valve shells; for it very often occurs on the outside of such 
shells, on stones, the back of Limulus, &c., and is frequently 
associated intimately with fornicata in all these situations; but 
nevertheless it always retains its essential characters, under all 
circumstances. The typical fornicata is also often found with 
it, plentifully, on the iszde of dead shells. 
Nor can Margarita acuminata be the young of J. varicosa ; 
for in our collection there are full-grown specimens of both, 
equal in size, from Labrador. 
There is no sufficient reason for adopting the name Lacuna 
divaricata in place of L. vincta; for it is not the Trochus divar?- 
catus of Linné (1767), although it is the shell described under 
the same name by Fabricius in 1780, as shown long ago by Dr. 
Stimpson and others. Fabricius made a mistake which we 
have no right to perpetuate; nor does ‘‘ usage,” to which Mr. 
Jeffreys so often appeals, sanction the change. 
The Lunatia triseriata is not, as Mr. Jeffreys thinks, the 
young of ZL. heros, but only a color-variety, as the writer had 
previously shown (April, 1872). Both varieties occur together, 
from the smallest to the largest sizes; but the former some- 
times becomes plain-colored before reaching maturity. There 
is no evidence that Natica clausa is the Nerita affinis of Gmelin, 
but quite the contrary ; for the latter was placed in the section 
of umbilicated species, was described as silvery within, and came 
from New Zealand! It is probably one of the Trochide, and 
certainly could not have been this emperforate Natica. 
In this place I shall not enter into a discussion of the numer- 
ous cases in which the author has reduced the American shells 
to “varieties” of the Huropean species, because in many of 
these cases there must long be great diversity of opinion, and 
for most purposes it matters little whether these closely related 
forms be called “ varieties” or ‘‘species,” so long as the actual 
differences are recognized. But since Mr. Jeffreys has evidently 
made so many important mistakes in his article in regard to 
the identity of species, and has united those that have no near 
affinities, as already shown, it is logical to conclude that he 
may have made other mistakes in the case of more critical 
species. He must therefore pardon us if we regard his decisions 
in all these cases as at least doubtful, until confirmed by other 
evidence. 
