,188 
I am under the necessity of changing the name which I first 
applied to this shell, that of elongatus being preoccupied by Bra- 
parnaud for a very different species. 
The fold of the columella is much less profound than that of L. 
palustrisy L., which it resembles. PI. 31, fig. 1. 
Limneus E.ELEXUS. — Limneus rejiexuSj noh. Journ. Acad. 
Nat. Sci.y vol. 2, y?. 168. 
PI. 31, fig. 2. 
Limneus eludes. — Limneus elodes, noh. Journ. Acad. Nat. 
Sci., vol. 2, j9. 169. 
Limneus palustrisj L. f 
Ohs. The fold of the columella is much more profound than 
that of umhrosus. 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. SillimaJs Journal, vol. %,No. 2,p. 
267, IS, fig. 14, a, h, c. 
Unio ovatus, var. h, Lam. Anim. Sans. Yertehr.,vol. 6, y>. 76. 
Unio occidens f Lea. Trans. Amer. Philos. Soc., New Series, 
vol. 3. 
Desc. Shell with the anterior side very broad, sub truncate ; 
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 chest- 
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.^^ 
Ohs. I quote the above description from Barnes’ very useful 
essay On the genera Unio and Alasmodontafi in which this 
