230 
dermis wliicli covers tlie exterior. A specimen now before ns^ 
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, Eaf — Desc. 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 truncataj Raf. Ann. gem. des Sc. Pliys., vol. 5. Poulson's 
translation, p. 31. 
Unio elegans, Lea. Trans. Amer. Phil. Soc., neiv series, vol. 4, 
p. 83, p/. 9, fig. 13. 
Ohs. This shell inhabits the Wabash, Scioto, Ohio and other 
western rivers. PI. 67. 
Unio lineolattjs, Specific character. Sub triangular, 
disk and umbo much depressed ; beaks simple, prominent. 
Unio lineolata ; Unio depressa, (jjoung,') Raf. Ann. gen. des 
Sc. Phys., vol. 6. Mr. Poulson’s translation, p. 35. 
Unio securis. Lea. Trans. Amer. Phil. Soc., new series, vol. 3, 
p. m,pl. llyfig. 17. 
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 arquated, 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. 
