NO. 1205. S YNO PSfS OF THE NA I A DES SIMPSON. 757 



radial, roughened; laterals short, heavy, nacre white, brilliantly irides 

 cent posteriorly ; beak cavities shallow. 



Animal apparently having ovisacs in pairs which are slightly wavy 

 and lirate at the base; gills rather large, semicircular, inner much the 

 larger, partly free from the abdominal sac; mantle thin, thickened at 

 edge, and bordered with a dark line. 1 



t PLEUROBEMA SHOWALTERII Lea. 



* Unio showalterii LEA, Pr. Ac. N. Sci. Phila., IV, 1860, p. 307; *J1. Ac. N. Sci. 



Phila., V, 1862, p. 73, pi. vm, fig. 223 ; Obs., VIII, 1862, p. 77, pi. vm, fig. 223. 

 *SOWERBY, Conch. Icon., XVI, 1868, pi. LXXXI, fig. 426. *B. H. WRIGHT, 

 Check List, 1888. * P.ETEL, Conch. Sam., Ill, 1890, p.167. 



* Mar gar on (Unio) shou-alterii LEA, Syn., 1870, p. 55. 



Coosa Eiver, Alabama. 



(Group of Pleurobema nux.) 



Shell oval, inflated, moderately solid, with a low posterior ridge, 

 swollen at the post-basal part; posterior end pointed at the termi- 

 nation of the posterior ridge; beaks full, rather high, considerably 

 removed from the anterior end ; epidermis pale to dark brown, rest 

 lines very distinct; pseudocardinals small, stumpy, radiate, rough, 

 laterals straight; nacre brilliantly iridescent posteriorly; front part of 

 shell heavy, suddenly becoming thinner behind. 



Animal unknown. 



t PLEUROBEMA VERA Lea. 



*Unio verm LEA, Pr. Ac. N. Sci. Phila., V, 1860, p. 140; Ml. Ac. N. Sci. Phila., V, 

 1862, p. 83, pi. xi, fig. 231; * Obs., VIII, 1862, p. 87, pi. xi, fig. 231. *B.II. 

 WRIGHT, Check List, 1888. 



*Margaron ( Unio) verus LKA, Syn., 1870, p. 38. 



Black Warrior and Cahawba rivers, Alabama. 



t PLEUROBEMA HAGLERI Frierson. 



* Unio (Pleurobema) hagleri FRIERSON, Nautilus, XIII, 1900, p. 109, pi. u, 

 North River, Alabama, near Tyner. 



t PLEUROBEMA RUBELLA Conrad. 



* Unio rubellits CONRAD, New F. W. Shells, 1834, p. 38, pi. vi, fig. 2, p. 71. *FERUS- 



SAC, Guer. Mag., 1835, p. 29. *MOLLER, Syn. Nov. Gen., 1836, p. 205. ^IAN- 

 LEY, Test. Moll., 1842, p. 201 ; *Biv. Shells, 1843, p. 201. *CHENU, Bib. Conch., 

 Istser., Ill, 1845, p. 20, pi. n, fig. 2. *CATLOWand EEEVE, Conch. Norn., 1845, 

 p. 63. "CONRAD, Pr. Ac. N. Sci. Phila., VI, 1853, p. 257. *H. and A. ADAMS, 

 Gen. Rec. Moll., II, 1857, p. 492. *B. H. WRIGHT, Check List, 1888. T.KTKI,, 

 Conch. Sam., Ill, 1890, p. 166. 



1 The single species which I place in this group is quite variable. Some specimens 

 iipliroach Quadrula solida and trigona in general shape, while others are more like 

 / leurobema irrasa and troscheliana. I judge from the character of the gills that the 

 inarsupium is confined to the outer pair. 



