* 
50 W. Stimpson on the so-called Melanians of N. America. ; 
_ Ata meeting of the Academy of Natural Sciences of Phila- 
delphia, in February, 1863,” Dr. Lea “read part of a letter from 
Dr. Lewis, of Mohawk, New York, in which he said that he was 
ratified with one thing, which was not apparent to him at first. 
n his notes on Melania subularis Lea, and M. exilis Hald.,two | 
shells. Dr. Lewis thinks the sinus in the sides of subularis is 
peculiar, and will be found in the whole group of Trypanostoma 
and the granular sides of exilis in the whole group of Goniobasis.” 
ave here a proposition to consider the lateral sinus, which 
is now demonstrated to be a sexual difference, as a generic char- 
acter. This simply shows how necessary it is to become ac- 
quainted with the general structure of the animals we investi- 
gate, before studying their generic and specific relations. : 
In connection with the subject of the relations of this sinus, 
it may be remarked incidentally that Dr. Lewis, in a paper pub- 
lished in 1861," gives a description of the so-called Amnicola 
lapidaria (Pomatiopsis), stating that the soft parts in this species 
are “identical in form with Jfelania ;” and in the paperin the | 
Proceedings of the Academy of Natural Sciences of Philadelphia = & 
above cited, he gives a detailed account of his reasons for refer- 
ring the species to the neighborhood of Melania, basing them 
chiefly upon the similarity in the movements of the animal, and 
in “the expansions and contractions of the foot in progressing.” 
Dr. L. was here probably misled by the resemblance of certain 
sinuses in the sides of the foot of Pomatiopsis lapidaria, to that 
seen in the females of the Melanians. But the sinuses in the 
Pomatiopsis are of an entirely different character, having no re- 
lation to the sexual system, and being. the result of a peculiar . 
arrangement of the muscles, by which the “looping” method of 
progression on dry land, characteristic of that animal, is effected ; 
and they occur on both sides of the body, and exist, of course, 
in both sexes. 
We now come to the paper of Mr. Theodore Gill, published 
in the Proceedings of the Philadelphia Academy of Natural 
Sciences for 1863. This: writer (I. ¢., p. 84) alludes only inci- 
dentally to the Melanians, following bis predecessors in consider- 
ing them to form a distinct family, which he has, however, re- 
stricted in a far more natural manner than had been previously 
done, as he 
to it. He has also 
from the Old- World 
g orms formerly referred 
for the first time separated the American 
Melanians; saying, ‘‘The American Mela-_ 
sub-family, Ceriphasiine,” and (note under 
wig 
