﻿49^ AI.ASMIDONTA 



I cannot 1)\ any ]>ossibilit\ separate this from Lea's Mar- 

 ^aritcna drltoidra. l^ea says that the drlfoidca is smaller, 

 more trianj^ular and llattened and that the undulations of the 

 beaks are unliroken. There seems to be every possible varia- 

 tion between these extremes of beak sculpture, sometimes oc- 

 cu rrinof in a lot from the same locality ; the larger shells have 

 both kinds of sculpture and while the form is usually decid- 

 edly rhomboid, there occurs every variation to specimens that 

 are nearly elliptical. 



r 



Alasm iDON TA M I NOR ( Lea ) . 



Shell small, rhomboid, convex, somewhat inequilateral, witb 

 moderately full but not high beaks, their sculpture a few coarse 

 ridges running parallel witli the growth lines, with radial 

 threads in front of and behind them ; posterior ridge low or 

 moderate, rounded, ending behind in a widely rounded point 

 at the base ; surface with uneven growth lines ; epidermis 

 greenish-yellow with broad and narrow wavy green rays, the 

 yellow spaces between them often narrower than the rays, the 

 whole lusterless; left valve with a strong, double or triple 

 tooth ; right valve with one strong tooth under the beak ; lat- 

 erals faint and blurred ; nacre bluish-white, sometimes dirty 

 straw-colored, a little thicker in front. 



Length 39, height 25, diam. 14 mm. 



Length };/, height 22, diam. 15 mm. 



Tennessee and Cumberland River systems. 



Type locality. North Carolina. 

 Margaritana minor Lea, Pr. Am. Phil. Soc, I\', 1845, p. 166; 



Tr. Am. Phil. Soc. X. 1848, p. 82, pi. viii, fig. 26; Obs.. IV, 



1848, p. 56, pi. VI II. fig. 26. — Chenu, Man., 1859, N, p. 144, 



fiR- 7T3- 

 Stropliitiis minor Coxrad, Pr. Ac. N. Sci. Phila., \'L 18^3, p. 



263. 

 Margaroii (Mariiaritana) minor. Lka. Syn., 1852, p. 42: 1870, 



p. 67. 

 BapJiia minor TT. and A. .-Xdam.s. Gen. Rec. Moll.. IT, 1857, p, 



400. 

 Alasmidonta minor Simpson, Syn.. T900, p. 668. 



