142 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
Abundant with the preceding. Relatively more abundant in less 
brackish water. Extremely variable here as elsewhere. 
0 
Rissoidae. 
% 
Ilissoa minuta (Totten). Smith and Prime (’70), p. 393. 
jLittorinella m. Verrill (’73), p. 653. N. 
Very common on Ulva and in black mud, upper harbor, in water 
almost fresh. 
Ilissoa laevis (DeKay). Smith and Prime (’70), p. 393. Litto- 
rinella l. Yerrill (’73), p. 653. Hydrobia ? 1. Yerrill (’82), p. 523. 
? Rissoa stimpsoni Smith. Smith and Prime (’70), p. 393. 
This and the preceding and two succeeding species are in such 
confusion as scarcely to repay any attempt to straighten out the 
nomenclature without further knowledge. Stimpson (’65) on the 
strength of the dentition and anatomy of 11 . minuta retained 
the genus Littorinella in his subfamily Hydrobiinae (= Amni- 
colinae of Gill) distinguished from Rissoinae on dentition alone, 
but suggested a new genus — Ecrobia — which Fischer (’87) adopts. 
The shell has also been referred to Paludinella, Cingula, and 
Hydrobia. As to 11. laevis the case is much worse, for not only 
does it share the above changes but sometimes one appears in one 
genus or family and the other in another, while in truth the specific 
difference of the two is at least doubtful. As the' dentition and 
anatomy of JR. laevis have never been examined (so far as I know), 
any attempt to deal with the matter must be a guess. All that is 
said here applies to the two succeeding species. Dali recognizes 
only minuta , which he assigns to Rissoa, section Cingula. Whatever 
may be thought of the generic classification, the ignoring of the 
specific complications seems justified. Out of the hundred or so 
specimens examined from Coldspring Harbor two answered to 
• the description of JR. laevis ; a few answered to the description 
of 11 . stimpsoni better than to that of 11 . minuta , while many 
answered equally to either; one answered better to the description 
of 11. latior than to either of the others. It seems to be true 
* 
that these variations (?) are local and that connecting series are 
not very complete. 
? Ilissoa stimpsoni Smith. Smith and Prime (’70), p. 393 c 
Yerrill (’82), p. 523. ? Littorinella laevis Yerrill (’73), p. 653. 
Cf. supra. 
