430 Annals of the Carnegie Museum. 



As has been stated above, the Nearctic Sphaeriid fauna is still 

 very imperfectly known; yet the material now at hand proves it to 

 be surprisingly rich in groups, species, and forms, when compared 

 with what was known some years ago. It is much more so than the 

 Palearctic, a fact which is explained by the geological history of the 

 continent. The two faunas are more closely related than has been 

 supposed, e. g., by Clessin; the genera are the same in both, quite 

 a number of species are identical, and others are at least close relatives. 

 More e\idence in that direction may come to light when the ^•ast 

 territory of British America is better explored, being in the same lati- 

 tude as middle and northern Europe. 



The metropolis of the Nearctic Sphseriida^ is the region of the Great 

 Lakes, where they have attained the greatest number of species and 

 the widest diversity of forms. The East, and more so the West, have 

 a number of species and forms of their own, which present some 

 apparently difficult problems of distribution. The South has some 

 species which show relations to the faunas of the West Indian islands 

 and of Central and South America. 



The fauna of our Great Lakes themselves is only fragmentarily 

 known, so far as the SphcCriidae are concerned, strange as it may 

 appear. To judge from the material at hand, from a few places on 

 Lakes Michigan and Erie, and from very little dredging, there are 

 many peculiar forms, and possibly species. It is hoped that systematic 

 collecting may be done at many places, so that it may be possible to 

 ascertain the relations of the forms from the lake-region with the 

 species and forms from other regions and also to compare the faunas 

 of the several lakes. 



In the following catalog an attempt is made to give a sur\-ey of 

 our knowledge of the group so far as this can be efifected by a mere 

 list. To the species cited from previous literature a few new ones 

 are added, together with some varieties, most of which were established 

 and named years ago. It may be added that there are numerous 

 forms in the hands of the writer, which could not be referred to any 

 of the established species. With additional material for comparison, 

 the affinities of these will eventually be ascertained. 



With every species citation is made of the publication in which it 

 was originally described. Other papers, some of which are more 

 easily accessible, or which are desirable for reference in order to a 

 better understanding of the species, are also in some cases cited. 



