118 PROCEEDINGS OF THE ACADEMY OF [1888. 



slightly emarginate, and raised into a distinct and angled carina, 

 which is thin and compressed. Ligamental area often with several 

 small plicfe. The posterior end is generally sharply compressed 

 above and below, giving it a lance-shaped and ancipital appearance. 

 Urabonial ridge depressed, narrow, and rounded. Anterior margin 

 rounded and slightly oblique, basal margin convex. Epidermis 

 yellowish-brown or olive colored, or even bright green, with slender 

 green rays in uneven fascicles, or rayless and reddish-brown all over. 

 Umbos very much flattened, and beaks very small and pointed, hav- 

 ing a few concentric folds. Cavity of the beaks nearly obsolete. 

 Dorsal cicatrices small and deep. Cardinal teeth oblique and very 

 small. Lateral teeth long, thin, undulated and nearly straight. 

 Nacre salmon or purple, or both mixed. Shell darker behind and 

 at the base. 

 Diameter .75. Length 1.12. Breadth 2.30 inches. 



Habitat. Lake Woodruff', Volusia Co., Florida. 



Mus. Acad. Nat. Sciences. Cornell University. National Mus. 



lieinarks. The left beak is often shorter than the other. Its affin- 

 ity is with U. viridicatus Lea, which has much larger cavities under 

 the beaks, the lateral teeth coarser and not undulating and the an- 

 terior end not obliquely rounded, and is not rayed. It cannot be 

 mistaken for U. Jayanus Lea. We have great pleasure in dedica- 

 ting this species to Mr. Charles T. Simpson of Ogallala, Nebraska, 

 who has done very much in studying the mollusca of Florida. 



Unio Marshii. Plate V, fig. 2. 



Shell somewhat narrow-elliptical, transverse, veutricose and very 

 inequilateral, smooth, incremental lines close and slightly raised. 

 Substance of the shell rather thin, and of very uniform thickness; 

 swollen in the umbonial region ; umbonial slope rounded ; posterior 

 slope compressed and rounded ; dorsal margin nearly straight ; an- 

 terior margin abruptly rounded ; basal mai'gin much excurvate and 

 slightly constricted near the posterior extremity ; posterior margin 

 bluntly rounded and emarginate above ; turned up, raised into a 

 very small, depressed, and thin carina. Beaks blunt, broad, with- 

 out concentric undulations but possessing three or four raised, radiat- 

 ing lines; epidermis remarkably thin, reddish brown below and green- 

 ish above, indistinctly and closely rayed over the anterior portion, and 

 very darlc or black on the posterior slope; nacre, a beautiful salmon 

 varying to ])urple ; cardinal teeth compressed, erect, striate, very 

 oblique and disposed to be double in both valves ; lateral teeth long. 



