20 THE NAUTILUS. 



Anticosti Is., Albany river, Ontario (W. Mclnnes ed., both sent by 

 J. F. Whiteaves); "Vineyard," Pawtuxet, R. I., (J. F. Perry); 

 several places in Aroostook co., Me., (0. P. Nylander); Pine river, 

 Marquette co., and Oswald Lake, Mich. (B. Walker); Isle Royale, 

 Mich. (University of Michigan ; some other specimens from waters 

 on the same island were under doubt). Specimens from Union 

 springs, Ontonagon Co., Mich. (B. Walker), are of somewhat differ- 

 ent shape: the beaks are more posterior and narrower, and the an- 

 terior end is less broadly rounded. One good specimen was among 

 fossils from Arnold's Lake, Washtenaw Co., Mich. (B. Walker.) 



Examples of this Pisidium had been in hand for years, un- 

 named, or a part doubtfully referred to other species. Since last 

 year, several good lots from widely distant places came in and proved 

 the species to be valid. 



Pisidium friersoni n. sp. Mussel rather small, moderately in- 

 flated, outlines somewhat angular ; superior margin slightly curved 

 or nearly straight, with projecting, rounded angles where passing into 

 the supero-anterior and the posterior, which are well marked, and 

 nearly straight, inferior moderately curved ; beaks scarcely posterior, 

 projecting over the hinge margin, rather narrow, with a somewhat 

 flattened central area ; surface with very fine, subregular striae, dull- 

 ish to somewhat shining, color pale horn to straw or whitish, shell 

 translucent to opaque, thin, hinge comparatively rather stout ; right 

 cardinal tooth curved, its posterior end thicker and grooved, left 

 anterior quite short, somewhat V-shaped, posterior rather short, rather 

 steep oblique ; outer laterals of the right valve distinct ; ligament short. 



Long. 4, alt. 3.5, diam. 2.5 mill. 



Hab. : Louisiana, Texas, New Mexico, Colorado. — In 1899, Mr. 

 L. G. Frierson sent me quite a number of specimens at all stages of 

 growth, collected at Frierson, La. ; they were regarded as repre- 

 senting a distinct species, but shelved. Since then I have seen the 

 same from Dallas (Cincinnati Museum) and Comal Co., Tex., the 

 Gallinas river, Las Vegas, N. Mex., and a few from Denver, Colo., 

 (T. D. A. Cockerell). 



The species seem to range under the group of P. noveboracense 

 Pr., and so far as known, shows little variation. It has been named 

 in honor of Mr. L. G. Frierson. 



Erratum. — Nautilus, February issue, p. 119, line 2 from top: 

 after even, there should be a comma. 



New Philadelphia, Ohio. 



