1004 NODULARIA 
Unio nuttallianus Lea, Pr. Ac. N. Sci. Phila., VIII, 1856, p. 
103 ; Obs., V5 1857,"ps 30; pl. xxx hee 25): [lave Nien: 
Phila., III, 1858, p. 310, pl. xxx, fig. 25—Hantey and 
THEOBALD, Conch. Ind., 1876, p. 19, pl. x1, figs. 5, 6. 
Margaron (Unio) nuttallianus Lea, Syn., 1870, p. 74. 
Nodularia nuttalliana SiMPSON, Syn., 1900, p. 817. 
More solid and rather shorter than N. olivaria, to which it 
is apparently closely allied. The epidermis is yellowish-green 
with light bands and is not milky, the nacre is differently col- 
ored and in the specimens examined has a dark, bluish blotch 
in the cavities of the beaks. All the specimens I have seen 
have the beaks slightly eroded, but they exhibit no traces of 
sculpture. 
NODULARIA INVOLUTA (Benson). 
Shell irregularly ovate, slightly inequilateral, compressed 
behind, swollen below the umbonal region, thin, polished ; pale 
green obscurely radiate with yellowish, bluish above, polished, 
with two or three dark rays on the dorsal slope; beaks very. 
high and full, with a few light corrugations; anterior end 
narrowly rounded above, cut away below; base rounded and 
full about the middle, slopingly cut away behind to a point on 
the median line; posterior ridge low; pseudocardinals elevated ; 
laterals large, lamellar; nacre silvery. 
Length 44, height 30 mm. 
Assam. 
Unio mvolutus Benson, Hanley Biv. Shells, 1856, p. 385, pl. 
Xx, fig. 19.—Hanriry and THrosparp, Conch. Ind., 1876, 
ps ro, pli xuiyshes 2: 
Margaron (Unio) involutus Lea, Syn., 1870, p. 37. 
Unio involuta SowERsBy, Conch. Icon., XVI, 1866, pl. xxxIv, 
Ag: 177; 
Nodularia involuta Stwpson, Syn., 1900, p. 817. 
Differs from N. olivaria in being more ovate, in having much 
higher beaks, which, according to Hanley, have some sculpture, 
in being cut away at the anterior base, and having rays. A 
