XIII. SOME NOTES ON SPH^RIID^ WITH DESCRIP- 

 TIONS OF NEW SPECIES. 



By Victor Sterki.^ 



Among the Sphseriidee examined by me during the year 1919 there 

 were an unusual number of forms possessing interest in regard to 

 their systematic position and distribution, and there are also some 

 new species and forms. 



At the Biological Station of the University of Michigan, on Devils 

 Lake, North Dakota, as headquarters, Miss Mina L. Winslow, of the 

 Museum of Zoology, and other collectors have secured some good 

 material, which they sent me for examination. It mainly consists of 

 Sphccriid(s, VaUonia, and PupilUdcc. I mention some of their send- 

 ings in the following paragraphs. 



1. Vicinity of Devils Lake, North Dakota: Pisidium temiissimiim 

 Sterki, a very small form from several unnamed lakes, and from 

 Court Lake; P. tenuissimum calcareum, a form frequent to common, 

 occurring fossil in the marls of Maine, Michigan, and Illinois, but 

 now for the first time represented by recent specimens ; a few speci- 

 mens of P. vcsiculare, a small form from the same localities. 



2. Turtle Mountains. North Dakota, from which nothing had been 

 before this reported: P. variahilc, paiipcrcnhnn, contortum Prime, the 

 last mentioned not before seen from west of Michigan ; P. apiculafum 

 n. sp. (see infra, Description No. 7) ; and an exceptionally small form 

 of P. comprcssiim Prime. 



3. There are six separate lots taken from the Sheyenne River at 

 various places. Of particular interest are Sphcerium declive n. sp. 

 (see infra, Description No. 12) ; 6". sulcatum Lamarck, the same form 

 as from South Dakota ; a few valves of a small Sphcerium, apparently 

 stamineum Conrad, which call for more specimens for their exact 

 determination ; Muscidimn jayensc Prime. Most of the specimens 



1 This paper is part of a report submitted to the Director of the Carnegie 

 Museum about the beginning of the year 1920. 



425 



