834 QUADRULA 
Unio (Theliderma) cylindrica SwAINson, Treat. on Mal., 1840, 
pe 27 tig 5 4c. 
Quadrula cylindrica SIMPSON, Syn., 1900, p. 773. 
Unio (Eurynia) solenoides var. cylindrica RAFINESOUE, Ann. 
Gen. Sci. Phys.’ Brux., V, 1820; p. 208. 
Umio nawiformis LAMARCK, An. sans Vert., VI, 1819, p. 75.— 
VALENCIENNES, Rec. Obs. Zool., IJ, 1833, p. 233, pl. Lut, 
fig. 4.—Rreve, Conch. Syst., 1841, p. 118, pl. Lxxx1x, fig. 7. 
Umo rugosus CHENU, Man., 1859, II, p. 138, fig. 668. 
This is perhaps the most beautifully painted Naiad in the 
world. Occasional specimens are uniformly colored, but a 
great majority have a lovely pattern of green angular markings 
on a lighter ground. The form is an aberrant one and can 
never be mistaken for any other. 
Mr. BR. H. Wright, Nautilus, XII, 1898, p. 6, has made a 
var. strigillatus of a compressed, very rough form of cylindrica. 
There seems to me to be an absolute graduation from cylin- 
drical, nearly smooth specimens to this form. 
QUADRULA METANEVRA Rafinesque. 
Shell irregularly rhomboid, more or less inflated, solid, in- 
equilateral; beaks rather full and high, turned forward over 
a narrow lunule, their sculpture a few strong, irregular ridges, 
which are nodulous on the posterior ridge; posterior ridge ele- 
vated. rounded, separated from the rest of the shell in front 
and behind by a radial depression; anterior end rounded ; base 
line straight or incurved behind the middle; dorsal slope ob- 
liquely truncated, the sulcation above the posterior ridge end- 
ing in a well-marked sinus; surface more or less covered with 
lachrymose knobs or tubercles, a row on the posterior ridge 
usually higher; epidermis yellow-green, tawny or brownish, 
often marked with small, dark green, triangular patches, sub- 
shining to dull and rough; pseudocardinals ragged, two in the 
left valve and three in the right; laterals short ; anterior scars 
small, impressed ; beak cavities deep, compressed ; nacre white, 
rarely pinkish, greatly thickened at the anterior base. 
Length 100, height 72, diam. 55 mm. 
