394. Miscellaneous. 
Amnicola, Gould & Hald., Bythinella, Moq.-Tand., Stenothyra, 
Benson, Tricula, Benson, Pyrgula, Christ. & Jan, Paludestrina, 
D’Orb., Tryonia, Stim., Potamopyrgus, Stim., Lithoglyphus, Mihl- 
feld, Fluminicola, Stim., Gillia, Stim., Somatogyrus, Gill, and 
Cochliopa, Stim. 
6. Pomatiopsine, including Pomatiopsis, Tryon. 
The memoir is mainly devoted to the subfamilies Hydrobiine and 
Pomatiopsine. Of the genera belonging to the former, extended 
descriptions, and excellent outline cuts illustrating the shell, animal, 
dentition, &c., are given of the typical species of Amnicola, Bythinella, 
and the new genus Fluminicola. Similar illustrations and a good 
description are given of the type (Amunicola lapidaria, Say) upon 
which the genus Pomatiopsis and the subfamily Pomatiopsine were 
founded. The latter type, although a true air-breathing mollusk, 
living habitually out of water, is shown to breathe by gills, and not, 
as would naturally be expected, by lungs. He remarks, however, 
that ‘it may be said to be amphibious, but only in the sense that 
Suecinea and some other terrestrial mollusca are so; that is, it is 
capable of living for a long time under water.” ‘The foot of this type 
is also shown to be adapted, by a peculiar construction, to a gliding 
mode of progression in water, and to a stepping motion, aided by the 
rostrum, when on land. 
Further on, he gives an extended description of the subfamily 
Hydrobiine, with accurate diagnoses of each of the included genera, 
full references, synonymy, citations of types, &c. Of these genera, 
the following are new :—Tryonia, Stim., founded upon a new species; 
T. clathrata (probably extinct) from the Colorado desert; Pota- 
mopyrgus, Stim., founded upon Melania corolla, Gould ; Cochliopa, 
Stim., founded upon Amnicola Rowellii, Tryon ; Gillia, Stim., founded 
upon Melania altilis, Lea; and Fluminicola Stim., founded upon 
Paludina Nuttalliana, Lea. 
It is worthy of note that the author has not, as is too often done, 
gone on to refer by guess, to his new genera, all the little shells that 
might be supposed to belong to them, but leaves that to be done by 
others who may have an opportunity to study thoroughly their softer 
parts, dentition, &c., and determine whether or not they really possess 
all the characters of the newly founded groups. 
Another commendable feature in this memoir is, that the author 
has in each instance distinctly stated what species he regards as the 
types of thenew genera. Every naturalist must be aware that much 
of the confusion in the nomenclature of natural history has arisen 
from the neglect of this simple rule in the subdivisions of the group 
which may afterwards take place, some retaining the original name 
for one group of the species, and others for others, with no chance 
of agreement. Many, perhaps the majority, say that in such cases 
the old name should always be used for the group including the first 
species, or, in other words, that the first species mentioned or de- 
scribed under the old name should be regarded as itstype. Others, 
however, insist that the original name should be retained for the 
group including the majority of the species first described or inclu- 
