— 14 — 



146. Sphaerium securis* Prime. var. cardissum 



Prime, Pools and ditclies. Few specimens arr 

 mature in spring and early summer; m<.st are 

 small to half grown, but from last year, as evident 

 from the thick, dark deposit and algae growing on 

 the shells; Sph. partumeium living in the same 

 places with them, are clean, or little coated. 



147. PisiDiUM ABDITUM Hald. Common; variable, 

 a. var. . Smaller, more inflated. 



148. PisiDiUM VARiABiEE Prime. Scarce; near New 



Philadelphia; pool on the river. 



149. PISIDIUM COMPRESSUM Prime. Common in the 



river, the creeks and the Ohio canal; variable in 

 shape and striation. 



150. PISIDIUM . n. sp. River; common in some 



places. Of the same general appearance with P. 

 compressum, together with which it is found, but 

 constantly different: smaller, of a somewhat differ- 

 ent shape, flner^ but sharper striated, color more 

 greenish-horn, nacre thiri^er, transparent, colorless, 

 not white; there are also differences in I he hinge.— 

 May be looked for in other sections, as a few spec- 

 imens were seen from Herkimer County, N. Y. 



151. PISIDIUM CRUCIATUM Sterki. Tuscarawas river, 



with the preceding. Found for the first time in 

 October and November, 1891, and again, though 

 scarce, in fall, 1893.— Mr. E. W. Roper, after seeing 

 it, agreed that it was a new species, of a peculiar 

 type. It is very small, its length hardly exceeding 

 two millimeters. Probably it has been found else- 

 where, but taken for the young of some other spe- 

 cies. 



^= This is often written "secure" ; the word is evidently not the adjective seem 

 (secure), but the noun securis (hatchet). 



