UNIO 539 
Mysca ovata Turton, Conch. Ins. Brit., 1822, p. 246; Man. 
Shells Brit. Is., 1831, p. 21, fig. 12—Swatnson, Treat. on 
Mal., 1840, p. 277, fig. 56. 
Mysca solida ‘Turron, Conch. Ins. Brit., 1822, p. 246, pl. xvi, 
fig: 2; Man. Shells Brit. Is., 1831, p. 22, fig. 13. 
Mya ovalis Monracu, Test. Brit., 1803, p. 34. 
Unio ovalis Brown, L, and F. W. Conch., 1836, p. tor, pl. xvii, 
nese: ilokec: Conch. 1644, p82, pl. xxx, figs. 12-14. 
Margarita (Unio) ovalis Lra, Syn. 1836, p. 35; 1838, p. 24. 
Unio muelleri RossMASSLER, Icon., VIII, 1838, p. 41, pl. x1, fig. 
BAT el loq2. pet, pl. Liv, fie 730, 
Umio pictorum Brown, Ill. Rec. Conch., 1844, p. 81, pl. xxx1, 
figs. 8-11. 
Close to U. pictorwm and in some cases it is well nigh im- 
possible to separate it from that species. In general it is not 
quite so elongated ; it is wider in proportion in front and nar- 
rower behind. There is sometimes a slight fulness in the pos- 
terior basal outline just behind the middle, but this is not so 
common or so pronounced as in pictorum. Occasionally the 
posterior point is elevated a little so that it will be found a 
trifle above the median line. "The muscle scars are nearly 
smooth, shallow in thin shells, and well impressed in solid 
ones. ‘The anterior end is often subtruncated and _ slightly 
angled above. 
Unto TuRTONI Payraudeau. 
Shell oblong, inclined to be slightly rhomboid, convex to 
subinflated, subsolid, rounded in front and rarely angled above, 
inequilateral; beaks slightly elevated, moderately full, their 
sculpture variable, consisting of a few corrugated, subnodu- 
lous ridges that show a tendency to be doubly looped; some- 
times the sculpture is faint and reduced to a few nodules; 
surface nearly smooth; epidermis pale yellowish-ash, ashy- 
brown, greenish below, yellowish-green or sometimes almost 
olive, usually rayless and showing the dark rest periods dis- 
tinctly ; left valve with two compressed, ragged pseudocardi- 
