FAMILY UNIONISE UNIO. 195 



This shell was presented to me by Dr. Budd, who obtained it from Dr. Newcomb, by whom 

 it was detected in the northern canal near Troy. Mr. Lea's specimens were from the Juniata, 

 and from the Schuylkill near Philadelphia. Its northern geographical limits are consequently 

 much extended. In the specimens before me, the double cardinal teeth become united into 

 one in the larger individuals. 



Unio alatus. 



Unio alatus. Say, Nicli. Encyclopedia, Vol. 4, pi. 4, fig, 2. 



U. id. Barnes, American Journ. Science, Vol. 6, p. 260. 



U, id. Adams, American Journal of Science, Vol. 10, p. 27G. 



Description. Shell large, varying from moderately thick to very thin and fragile, subtrian- 

 gular, generally gaping at the posterior part of the base, fuscous, wrinkled. Beaks not pro- 

 minent, placed very much on one side, and decorticated : base nearly straight. Hinge-margin 

 very oblique, rising near the termination of the cartilage into an alated projection, and form- 

 ing almost a right angle with the inferior slope, which is nearly equal in length ; often with 

 numerous tubercles within, which upon the gaping extremities are confluent : cicatrices very 

 rough. Teeth crenate ; the outer laminated one obsolete, only one in each valve being per- 

 ceptible. 



Color. Epidermis brownish ; within purple red. 



Length, 3" 8. Transverse diameter, 5 '5. 



This large and well characterized species was observed by Mr. Lesueur in Lake Erie. It 

 occurs also in Lake Champlain ; and Dr. Newcomb has obtained very fine specimens from 

 the Northern canal, near Waterford. 



Unio rectus. 



Unio recta. Lam. An. sans vert. Vol. 3, p. 669. 



U. prmlongus. Barnes, Amer. Jour. Sc. Vol. 6, p. 261, pi. 13, fig. 11. 



U. rectus. Lea, Tr. Am. Phil. Soc. Vol. 5, p. 26. Adams, Am. Journal Sc. Vol. 41, p. 276. 



Description. Shell thick, elongated, narrow, tumid, somewhat pointed in front, obtusely 

 rounded behind. Beaks little elevated : basal margin slightly compressed, and in old speci- 

 mens arched ; lateral tooth long and thin. 



Color. Epidermis blackish brown ; in young specimens, with yellowish radiations. 



Vertical axis, 2" 5 - 2'7; transverse ditto, 5*5 - 6*5. 



This specie? is found in Lake Champlain. 



25* 



