THE NAUTILUS. 21 



Habitat : A pond near Garrettsville, Portage Co., Ohio ; a brook 

 near Indian mounds, and a very small stream, Kent Co., Michigan. 



In December, 1901, Mr. Geo. J. Streator collected several hun- 

 dred specimens, most of them immature and young. They were re- 

 garded as a new species and named, but not published, waiting for 

 more materials. Since then Dr. R. J. Kirkland has secured over 

 three hundred specimens from the first named place in Michigan, and 

 half a dozen from the latter. Last March Mr. Streator has again 

 found a number of examples at Garrettsville, O. Most of the spec- 

 imens were incrusted with a ferruginous or blackish coating, some- 

 times very thick. 



This Pisidium is remarkable for the position of the beaks, which 

 are not posterior, a feature also found with Pis. medianum. The 

 species is somewhat variable in regard to size and shape ; the largest 

 specimen seen was 2.7 mill, long, and moderately inflated. There 

 is a more different form, found among the Ohio and Michigan speci- 

 mens, averaging smaller, 1.7-2.0 mill, long, comparatively shorter, 

 well inflated, with the anterior part a trifle longer than the posterior, 

 the anterior end subangular, the supero-anterior slope being slightly 

 marked, and the color is somewhat lighter. 



In one specimen of the more typical form from Michigan, the 

 beaks are low, flattened on top, or rather impressed, and with con- 

 centric, elevated ridges around the flattened areas, somewhat like 

 those of Pis. ferrugineum Pr. 



Pis. mainense n. sp. 



Published as Pis. walker i St. var. mainense St. in.the NAUTILUS, 

 XII., p. 79. Since then numerous specimens were collected in 

 Michigan by Dr. R. J. Kirkland from Reed Lake, Green Lake, Pine 

 Island Lake and Little Bostwick Lake, and proved distinct from P. 

 walkeri, which is widely distributed and fairly constant. Pis. main- 

 ense is considerably smaller, less elongate, less oblique, the anterior 

 and posterior parts are less disproportionate in size. The hinge is of 

 rather the same character as that of walkeri, but in the specimens 

 examined from both Maine and Michigan, the left anterior cardinal 

 tooth is rather longer, and the cusps of the laterals are more abrupt, 

 especially so in the left valve. 



Size : Long 3, alt. 2.6, diam. 2. 



Long 3.5, alt. 3, diam. 2.3. 



Long 3.7, alt. 3.1, diam 2.2 (L. Bostwick Lake). 



