120 PROCEEDINGS OF THE ACADEMY OF [1888. 



Bemarl:^. Tliere is an iiffinity of this species 'svith U. venustus 

 Lea, but is more comjiressed behind and is larger. It has been 

 largely distributed as U. Bnck/eyi, thus causing much confusion as 

 to what the latter really i'^. U. Buchleyl Lea, is more pointed be- 

 hind, not uncinate there nor emarginate on the basal margin. Its 

 umbos are farther forward and less elevated. Its greatest diameter 

 as Avell as greatest length, is just behind the beaks, while in XJ.DalUi 

 the greatest length is through the summit of the umbo 



It is named for Mr. W. H. Dall of the Smithsonian Institution. 



Unio Tryoni. Plate VI, fig. 2. 



Shell wide, narrow-elliptical, compressed posteriorly, thin, polished 

 above. Umbos slightly elevated, the beaks being close to the ante- 

 rior end, and in the young undulated ; epidermis brownish or grayish 

 black, raised into numerous fine scaly stride, roughish, rayless, or with 

 some capillary obscure rays near the centre of the valves. Dorsal 

 margin straight, posterior margin bluntly rounded or truncate, and 

 triangular ; often subemarginate above, basal margin slightly convex, 

 anterior margin broadly rounded. Cardinal teeth of the left valve 

 are long, erect and widely separated to receive the single wide tooth 

 of the right valve. The anterior tooth is shorter and less pointed 

 than the posterior one, and the lattq;.' is curved upward. Lateral 

 teeth very long, rather slender and nearly straight. Nacre livid or 

 light salmon colored and often with several dark-brown circular 

 spots. Cavity of the beaks very shallow. 

 Diameter 1.25. Length 1.75. Breadth 4 inches. 



Habitat. Lake Woodruff, Volusia Co., Florida, near De Leon 

 Springs. 



Mus. Acad. Nat. Sciences. Newcomb Collection. National Mus. 



BemarJcs. This species is much thinner and lighter than U. Oc- 

 mulgeensis Lea, with Avhich there is the affinity of outline. It is 

 much narrower than U. Buddkmus Lea, and its cardinal teeth are 

 not oblique as in the latter. It is lighter, more rounded before and 

 more attenuated behind, and has a much shorter hinge line. Some 

 forms of it approach U. Jayanus Lea. 



It gives us much pleasure to dedicate this species to the late Mr. 

 Geoi-ge W. Tryon Jr., author of " Manual of Conchology" and other 

 conchological works. 



