﻿IC8 I.AAIPSII.IS 



A piizzlinjj^ form which is i)robahly only a variety of vannx- 

 emensis. Lea's types of ohscura and sieglcriana are probably 

 the same, the latter being a younger shell. Lea has four young 

 shells bearing the latter name, and T have seen two or three 

 elsewhere, which may possibly not hv this, but a related, un- 

 (tescribed species. The young shells I have seen are very del- 

 icately rayed, the rays showing through at the posterior end, 

 and are certainly different from the young of vanuxemensis. 

 I cannot be positive whether these young specimens develop 

 into the mature siefleriana or not as I have not seen material 

 in all stages of growth. 



Lampsims prattii (Lea). 



Shell small, elliptical or obovate, rather thin, somewhat in- 

 flated, smooth and shining, yellowish-green or pale olive with 

 feeble rays ; beaks rather low, placed a little in front of the 

 center of the shell, their sculpture not seen ; there are two com- 

 pressed pseudocardinals in each valve, the upper in the right 

 valve small ; two short, straight laterals in the left valve and 

 one in the right ; beak cavities shallow ; muscle scars slightly 

 impressed ; nacre bluish, dirty purplish in the center, iridescent 

 behind, slightly thicker in front. The male shell is nearly reg"- 

 ularly elliptical ; the female has a well-developed post-basal 

 swelling, and both are bluntly pointed behind. 



Length 33, height 22, diam. 14 mm. 



Chattahoochee River. Georgia. 



Type locality, Chattahoochee River, Roswell, Cobb Co., Ga. 

 Unio prattii Lea, Pr. Ac. N. Sci. Phila., IL 1858, p. 166; Jl. 



Ac. N. Sci. Phila., IV, 1859, p. 206, pi. xxiv, figs. 88, 88a ; 



Obs., VII, 1859, p. 24, pi. XXIV, fig. 88, 880. 

 Margaron (Unio) prattii Lka, Syn., 1870, p. 45. 

 Lampsilis prattii Simpson, Syn., 1900. p. 550. 



A rather attractive little species, which has a somewhat dif- 

 ferent texture from any near allied forms. It is thinner and 

 more shining than z'anuxemensis, and the nacre is more iri- 

 descent behind than it is in that species. 



