370 OHIO STATE ACADEMY OF SCIENCE. 



sufficient reasons, and more might be cited. The reasons for my 

 arrangement of the Unionidce 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 Unionidse (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., Unio rosaceus De Kay, leibei Lea, 

 hippopceus 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 Sphagriidae and Gastropoda, a few lake forms 

 are also known, and more will be found. All mollusca of the lake 

 should be systematicallv 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 Unionidae. After repeated attempts 

 to work up keys for the Sphaeriidae, I had to give it up, mainly 

 on account of the almost endless variation of a large part of out- 

 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. 



