ee at Se SS aes ORES Pe SL ee es eA ee 
Mr. Barnes on the Genera Unio and Alasmodonta. 119 
“with a deep cavity beneath. In others, the beaks are flat, 
slightly elevated, having only a small cavity within. 
Varieties. 
(a.) Oval. Mr. Say’s book, pl. 1. fig. 8. 
(b.) Ovate. Mr. S. B. Collins's collection, nee Bek se 
do 
(g-) R 
(h.) Radiate. Mr. Say simaes Philadelphia, Ouis- 
consin 
(2. ) Unio, giganteus. Mississippi. Dr. Mitchill’s collection. 
(k.) Deeply folded. Maj. Delafield’s collection. 
(l.) With the cardinal tooth oblique. Mr. Collins’s col- 
lection. 
Variety (c.) has the beaks projecting and recurved : ci- 
catrices deep ; primary tooth deeply sulcate ; lateral tooth 
long, high, and crenulate. Itapproaches our Unio Undatus. 
he variety (t.) deserves particular notice. A single valve 
sent by Professor Douglass to Dr. Mitchill, weighs fifteen 
ounces. It is in every respect, a gigantic shell. The dis- 
tance between the points of the two lobes of the cardinal 
tooth, is one inch; the length of the lateral tooth, three 
inches ; diameter of the posterior cicatrix, one inch, and 
its depth one fourth of an inch. ‘This shell of which four 
specimens were obtained by the N. W. Expedition, might 
perhaps constitute a separate species under the designation 
of Unio Giganteus. It is three times the size of the i 
Unio Crassus, mentioned by Mr. Say and M. Lamarck. 
Three specimens. 
Diam. 2°9 Length, 4°38 Breadth, 7:2 inches. 
3°0 4°6 7-0 
31 47 7*1 are preserv- 
ed in Dr. Mitchill’s cabinet. Another specimen 
Diam. 2:9 Length, 49 Breadth, 7-0 and weigh- 
ing fourteen ounces, is preserved in Gev. Gast’ s collection, 
Detroit. Hab. The Mississippi near Prairie du Chien. 
Prof. Douglas 
Variety (k. has the Epidermis dark brownish red, and 
the shell is deeply folded like U. Plicatus. Hab. Lake Erie. 
