370 OHIO STATE ACADEMY OF SCIENCE. 
sufficient reasons, and more might be cited. The reasons for my 
arrangement of the Unionide are stated elsewhere. As to the 
terms NEPHROPNEUSTA and BRANCHIOPNEUSTA: Von Ihering has 
found that the pulmonal cavity of the former has developed in 
connection with the nephridium, and they are related with the 
Nudibranchiata, that of the latter from the branchial cavity of 
the Tectibranchiata. Consequently, Stylommatophora and 
Basommatophora cannot be ranged, collectively, under one 
group, Pulmonata, as in contrast to the Prosobranchiata. 
Synonyms are added where it seemed necessary or advisable 
with respect to earlier lists and books to be consulted. 
Species introduced from other continents, are not an integral 
part of the Nearctic fauna, however interesting they may be, in 
several respects, and in order to mark this, their names are 
printed in different type (capitals). Certainly they swell the 
number of species recorded, but the number in itself is not of 
principal importance. It has been said that species and forms 
not identified, or of which descriptions have not yet been pub- 
lished, should not be included in faunal lists. In my opinion, 
they must be there, being parts of that fauna, and their syste- 
matic position and characteristic features should be pointed out. 
A few words may be in place with respect to the mollusca 
of Lake Erie Almost all Unionide (I have seen about thirty 
species, and there are probably more), are represented by forms 
more or less different from those of the rivers, generally being 
smaller, of different shapes, and often colors. Some of them have 
been described as species, e. g., Unto rosaceus De Kay, lerber Lea, 
hippopeus Lea; in fact they are varieties, lake forms, of Lamp- 
silis luteola, Obovaria circulus, Quadrula plicata, respectively. 
Corresponding forms of other species might, or should, be named 
and described. Of Spheriide and Gastropoda, a few lake forms 
are also known, and more will be found. All mollusca of the lake 
should be systematically collected, and compared with the 
inland forms as well as with those of the other great lakes. 
It has been suggested that keys for identification be added. 
I am sorry to say that this could not be done. Simpson states 
that it is impossible for the Unionide. After repeated attempts 
to work up keys for the Spherudz, I had to give it up, mainly 
on account of the almost endless variation of a large part of our 
species. For most of the Prosobranchiata, it would be equally 
impossible. For identifying the ‘“‘land mollusca’”’ of Ohio, keys 
have been published by the Academy*. A few species were 
added since, but they do not materially affect the keys. 
* In the fifth annual report, 1896, (by the writer); I have a number of 
copies, with additions, on hand, for distribution. 
