268 Descriptio7i of some neio Shells. 



the spark. When the battery circuit is complete through the in- 

 strument, the end a, of the armature is raised by the magnet, the 

 connexion is broken at c, and the end o, falls by its weight, again 

 rises, thus giving a rapid succession of sparks at c. The extrem- 

 ities of the armature are wound with a little sewing silk, or thread, 

 to prevent their retention by the magnet. 



Washington, November 13th, 1838. 



Art. YI. — Description of some neio Shells; by Benjamin Tappan, 

 Steubenville, Ohio. 



Prof. Silliman, — I send for publication in the Journal of Sci- 

 ence the following descriptions of some shells found in Ohio, 

 which are believed to be new. 



" Unio Sayii, Ward. Plate III. Fig. 1. 



Shell sub-rhomboidal, inequilateral, transverse, compressed ; 

 valves thin, beaks slightly prominent and divergingly wrinkled ; 

 cardinal teeth oblique, smgle in the right and double in the left 

 valve ; lateral teeth slightly curved ; nacre white. 



Hab. Walnut creek and Ohio canal, near Circleville. W. H. 

 Price. My cabinet ; cabinets of Dr. Kirtland, R. Buchannan, 

 Esq., B. Tappan, A. Binney, Esq., Dr. Gould, Dr. Jay, Col. Tot- 

 ten, &c., &c. ., 



Diam. 1. Length 1.60. Breadth 2.80. 



^hell inequilateral, transverse, sub-rhomboidal, compressed ; 

 posterior and superior margins rectilinear, basal margin curved, 

 anterior margin regularly rounded. Valves thin, translucent. 

 Beaks slightly prominent, incurved and divergingly wrinkled, 

 placed near the anterior margin. Umbonal slope sub-carinate, 

 carina somewhat elevated. Ligament long, narrow, nearly straight 

 and partially concealed. Epidermis pale yellow, inclining to cu- 

 preous on the umbos ; glabrous, with indistinct capillary rays of 

 a lighter color extending over the whole disk ; lines of growth 

 black, and very distinct ; two faintly impressed lines diverging 

 from under the points of the beaks and extending to the posterior 

 basal margin. Cardinal teeth very oblique, not prominent, single 

 in the right and double in the left valve, slightly crenate ; lateral 

 teeth lamellar, slightly curved. Anterior cicatrices distinct,, poste- 



