﻿rTYCHOBRANCHl^S 339 



Type locality, headwaters of the Black Warrior River, Ala. 

 Unio greeni Conrad, New F. W. Shells, 1834, p. 32, pi. iv, fig. 



I. — Conrad, Monog., VIII, 1837, p. 69, pi. xxxviii, fig. 2. — 



Hani.ey, Biv. Shells, 1843, P- 191 > P'- xxiv, fig. 6. — Chenu, 



Bib. Conch., 1st. ser., 1845, p. 17, pi. iii, fig. 5. — Sowerby, 



Conch, Icon., XVI, 1866, pi. xl,vii, fig. 253. 

 Margarita (Unio) greeni Lea, Syn., 1836, p. 24; 1838, p. 19. 

 Margaron (Unio) greeni Lea, Syn., 1852, p. 27; 1870, p. 42. 

 Ptychobranchus greeni Simpson, Syn., 1900. p. 614. 

 Unio simplex Lea, Pr. Am. Phil. Soc., IV, 1845, p. 163 ; Tr. 



Am. Phil. Soc, X, 1848, p. 76, pi. v, fig. 15 ; Obs., IV, 1848, 



p. 50, pi. V, fig. 15. 

 Margaron (Unio) simplex Lea, Syn., 1852, p. 27; 1870, p. 42. 

 Unio fJaz'escens Lea, Pr. Am. Phil. Soc, IV, 1845, p. 163; Tr. 



Am. Phil. Soc, X, 1848, p. 72, pi. in, fig. 9; Obs., IV, 1848, 



p. 46, pi. Ill, fig. 9. 

 Margaron (Unio) flavescens Lea, Syn., 1852, p. 27; 1870, p. 43. 

 Ptychobranchus Havescens Simpson, Syn., 1900, p. 614. 



Since writing the Synopsis I have seen some additional ma- 

 terial of the three forms I have placed together, and I can- 

 not find any good characters, on which to separate them. Lea's 

 Harescens is probably not mature and approaches foremani- 

 anum somewhat in form. His simplex, though not a large 

 shell, appears to be adult, and is somewhat more inflated than 

 Havescens. The species, as I recognize it. is smaller and more 

 delicate than foremanianum and is, on the whole, more nearly 

 elliptical in outline. 



Ptychobranchus subtentum (Say). 



Shell medium to rather large, elongate, slightly obovate and 

 subrhomboid, with a low, rounded posterior ridge ; narrowed 

 and rounded in front, solid, scarcely inflated ; surface smooth 

 and shining in young, and well preserved shells radiately pli- 

 cate or corrugated on the posterior slope, greenish-yellow or 

 yellowish-green, generally having a few broken, wide rays ; the 

 rays often break into square spots; at other times the markings 

 are zigzagged and nebulous ; left valve with two stumpy, small 



