230 



dermis which covers the exterior. A specimen now before us, 

 which we procured in the bay of Naples, exemplifies this singular 

 property. The present species is not uncommon in the West 

 Indies, and has been sent to us from Jamaica. Like all others of 

 this particular type, it is almost constantly covered with coralline 

 substances." PI. 66. 



Unio truncatus, Raf — Besc. Shell triangular, very convex, 

 gaping a little at the posterior extremity ; posterior lunule distinct ; 

 anterior margin very much flattened, forming a right angle with 

 the disk ; disk with an indented groove on the posterior side, ex- 

 tending from beak to base; anterior tip truncated; ligament slope 

 slightly grooved ; basal margin dilated in the middle ; anterior 

 margin slightly retuse ; epidermis olive yellow, radiate with green, 

 interrupted into short lines and spots generally sagittate ; within 

 white or rose-color ; cardinal teeth large and prominent ; muscu- 

 lar impressions small ; anterior impressions oval, impressed. 



Unio truncata, Raf. Ann. gem. des Sc. Phys., vol. 5. Poulso'n'.< 

 translation, jp. 31. 



Unio elegans, Lea. Trans. Amcr. Phil. Sac, new series, vol. 4, 

 p. SS,2^l. 9, Jig. 13. 



Obs. This shell inhabits the Wabash, Scioto, Ohio and other 

 western rivers. PI. 67. 



Unio lineolatus, Raf. — Specific character. Subtriangular, 

 disk and umbo much depressed ; beaks simple, prominent. 



Unio lincolata ; Unio dcpressa, (^young,^ Raf. Ann. gen. dea 

 Sc. Phys., vol. 5. Mr. Poulson's translation, p. 35. 



Unio securis. Lea. Trans. Amer. Phil. Soc, new series, vol. 3. 

 p. m, pi. 11, fig. 11. 



Desc. Shell subtriangular, surface brownish-yellow, with nu- 

 merous slender green radii and broader distant radii, frequently 

 composed of series of angular dark spots, with pale intervening 

 spaces ; disk and umbo much compressed ; beaks simple, promi- 

 nent, in the young acute at the apex ; anterior side subcuneiform ; 

 anterior margin regularly arquatcd, very much flattened, forming 

 a right angle with the disks ; posterior side short, obtusely rounded 

 at tip ; within white ; cardinal teeth very large, profoundly sulca- 

 ted and striated; lateral teeth inclining to be double in each valve. 

 Ohs. This species is common in the Ohio, Alabama, and Black 

 Warrior rivers. PI. 68. 



