258 MEMOIRS OF THE CARNEGIE MUSEUM. 



ToxoLASMA PARVUM (Barnes) (1823). 

 Lampsilis parva (Barnes) Simpson, 1914, p. 151. 



Plate XVI, fig. 3. 

 Records from Pennsylvania: 



Harn, 1891 (western Pennsylvania)."^ 



? Rhoads, 1890 (Beaver River, Wampum, Lawrence Co.)'*^ 



Ortmann, 19096, p. 191. 



Characters of the shell: Shell small, but rather solid. Outline subelliptical, 

 with the anterior and posterior ends almost uniformly and broadly rounded. 

 Lower margin gently convex or nearly straight, and almost parallel to the upper 

 margin. Beaks more or less inflated, slightly elevated above the hinge-line, located 

 anterior to the middle of the shell. Beak-sculpture distinct, consisting of five or 

 six comparatively strong, subconcentric bars, of which the later ones are sub- 

 angular behind. Valves more or less convex, often considerably inflated (chiefly 

 in the female), flattened upon the sides. No distinct posterior ridge. Posterior 

 slope flattened and somewhat compressed. 



Epidermis thick, dark, greenish, brown, or blackish, without rays. Growth- 

 rests not indicated by concentric bands. 



Hinge well-developed. Two pseudocardinals in left, one in right valve, tri- 

 angularly projecting, with rough edges. Interdentum absent. Laterals straight, 

 rather long, moderately strong. Beak-cavity moderately deep. Dorsal muscle- 

 scars in beak-cavity. Anterior adductor-scars distinct and well impressed, pos- 

 terior ones less so. Nacre silver}^ white. ^" 



Sexual differences present in the shell, but not very pronounced. As a rule 

 the male shells are less swollen, while the females are much more so (almost sub- 

 cylindrical). In the male the posterior end of the shell is narrower, sometimes 

 almost pointed, while in the female it is more broadly rounded and very blunt; 

 but there is great variability in this respect, and only in the older shells are these 

 differences unmistakable. 



L. H. D. 



Size: 1. Conneautlalie, Cat. No. 61.3534 32 mm. 19 mm. 1.5 mm. 



2. do. Cat. No. 61.4101 30 " 18 " 14 " 



3. do. " " do 27 " 17 " 11 " 



4. do. " " do 23 " 13 " 9 " 



Nos. 2, 3, and 4 are gravid females, and No. 1 also has the shape of a female. 



"^ Unfortunately Harn does not give exact locality, so that this record cannot be controlled. 

 166 Very likely incorrect, founded upon confusion with Eurynia fabalis. 

 '^' I have a few southern specimens, wliich have a faint pinkish blush. 



