448 Annals of the Carnegie Museum. 



13. Pisidium compressum coosaense Sterki. 



Pisidiiim compressum var. coosaense Sterki, Nautilus, XIX, 1905, p. 83. 



Also with rather coarse surface striae. 



Habitat. — Georgia, Alabama. Similar forms have been received 

 from Missouri and Oklahoma. 



14. Pisidium compressum contrarium Sterki. 



Pisidium compressum var. contrarium Sterki, Nautilus, XIX, 1905, p. 83. 

 Habitat.- — Georgia, Alabama. 



15. Pisidium compressum illinoisense var. nov. 



Mussel about as high as long, some specimens even higher; beaks 

 high, narrow, pointed, with rather small, but well-formed ridges; 

 balance of the mussel more rounded in outline than in typical or near- 

 typical P. compressum, less oblique, moderately inflated, markedly 

 flattened in the inferior part, generally even somewhat "pinched," 

 so that the margin is sharp, cutting; surface striae regular, sharp, 

 medium to fine, and crowded; color light to deep corneous, or brown- 

 ish; hinge slighter, laminae thinner, the posterior outer one of the 

 right valve quite small or vestigial. 



Habitat.- — Vicinity of Dubois, Washington County, Illinois, in a 

 reservoir and a pond, and in Sheller Lake, Jefferson County, Illinois. 

 Several thousand specimens were collected by Mr. A. A. Hinkley in 

 1908 and 1914. All are of the same shape, differing somewhat in 

 size and shade of color, but remarkably uniform in each habitat. It 

 is a peculiar form, having almost the significance of a species. 



16. Pisidium supinum A. Schmidt. 



Pisidium, supi-num Schmidt, Zeitschrift fiir Malacozoologie, VIII, 1850, p. 119. 

 Pisidium, supinum Clessin, Monogr. Cycladeen, in Martini-Chemnitz, 1879, p. 11. 

 Pisidium supinum B. B. Woodward, British Pisidia, 1913, p. 100, figs. 



Habitat. — Palearctic and Nearctic regions. Apparently rare in 

 North America; Lake Ontario, Ontario. Two fine specimens have 

 been seen by the writer in a collection labelled "P. noveboracense Prime, 

 U. 5." (Some other SphcEriidce, apparently from New England, were 

 also marked " U. S.") 



17. Pisidium henslowanum (Sheppard). 



Tellina henslowana Leach MS., Sheppard, Trans. Linn. Soc. London, 1825, p. 150. 

 Pisidium henslowanum B. B. Woodward, British Pisidia, 1913, p. 93, figs. 



