188 



I am under the necessity of changing the name which I first 

 applied to this shell, that of elongatus being preoccupied by Dra- 

 parnaud for a very different species. 



The fold of the columella is much less profound than that of L. 

 palustris, L., which it resembles. PL 31, fig. 1. 



LiMNEUs RELEXTJS. — Limneus reflexus, nob. Journ. Acad. 

 Nat. Set., vol. 2, p. 168. 

 PI. 31, fig. 2. 



Limneus elodes. — Limneus elodes, nob. Journ. Acad. Nat. 

 Scl, vol 2, p. 169. 



Limneus palustris, L. ? 



Obs. The fold of the columella is much more profound than 

 that of umbrosus. PI. 31, fig. 3. 



Unio ventricosus, Barnes. — Specific character. Shell large, 

 thick, triangularly ovate, convex ; umbones large, round, promi- 

 nent : beaks recurved ; cavity capacious. 



Unio ventricosus, Barnes. SilUman's Journal, vol. Q»,No. 2, p. 

 2Q7,pl l^,fig. 14, a, b,c. 



Unio ovaius, var. b, Lam. Anim. Sans. Vertebr.,vol. 6, jo. 75. 



Unio occidens ? Lea. Trans. Amer. Phihs. Soc, New Series, 

 rol. 3. 



L>esc. " Shell with the anterior side very broad, subtruncate ; 

 posterior side rapidly narrowed, subangulated ; disks very convex ; 

 umbones large, round, elevated ; beaks recurved over the liga- 

 ment ; ligament large and prominent, passing under the beaks ; 

 anterior lunule depressed at the margin, fuscous, broad heart- 

 shaped, longitudinally waved ; hinge margin depressed between 

 the beaks; posterior slope carinate; epidermis yellowish-olive, 

 becoming chestnut-brown on the umbones ; rayed with green, 

 more conspicuous in young specimens ; in old ones the dark ehest.- 

 nut-brown covers the whole and conceals the rays ; surface smooth 

 and shining, reflecting the face of the observer ; young shells are 

 splendent, having a much stronger lustre on the outside than on 

 the inside ; cardinal teeth broad, prominent and obliquely flatten- 

 ed ; lateral teeth broad, elevated, and terminating abruptly before ; 

 cicatrices large ; cavity of the beaks unusually large ; naker pearly 

 white ; surface smooth, but not highly polished." 



Obs. I quote the above description from Barnes' very useful 

 essay " On the genera Unio and Alasmodonta," in which this 



