16 RAFINESQUE’S 
94 Sp. ° Unio pallens, (Obliq. ditto. 1821.) Shell thick com- 
pressed, perfectly elliptic, both ends equal, hardly subtruncate ° 
behind, outside smooth pale yellowish, inside white. Length 3-5, 
diameter 3-10, axis 1-5 of the breadth. 
Ohio and Kentucky, rare, 2 or 3 inches. Lamellar tooth a little 
obliqual, short and thick, in the left valve furrow closed as in the G. 
Obovaria and Rotundaria. Yet an Elliptio which is the same as 
Ellipsaria. : 
95 Sp. Unio rivularis, (Obliq. ditto. 1821.) Shell rather thick’ 
swelled, perfectly elliptical, slightly arcuate below, outside brown 
and smooth, inside, bluish. Length 4-7, diameter 3-7, axis 2-7, of 
breadth. 
In the small streams of the Knob-hills and Cumberland mountains. 
Very small, hardly one inch. Lamellar tooth asin sp. 93.—Near 
to U. sinuata, sp. 67. 
96. Unio fontinalis, (Obliq. ditto. 1823.) Shell thick, rounded, 
triangular, sub-truncate behind ; quite rounded before and below; 
outside smooth, yellow, with some green spots; inside bluish white. 
Length 4-5, diameter 3-5, axis 2-5 of the breadth. 
At the spring of the source of Green R. in the Knob-hills, rare, 
very small, like a Cyclas ; but belong to 8. G. Scalenaria, lamellar 
tooth obliqual, straight, short. i 
[4] 
97 Sp. Unio chloris, (Obliq. chloris. 1823.) Shell oval obliqual, 
rather thick, and swelled ; the 3 sides rounded, outside greenish and 
smooth, inside bluish iridescent. Length 4-5, diameter 3-5, axis 1-5 
of the breadth. 
Small streams of Knob-hills. Minute shell, next to U. calendis 
Sp. 89, but distinct, lamellar tooth more curved, and not bisulcate. 
Both are Sintowia. 
98 Sp. Unio castaneus; [Obliq. and Aximedia, 1823.] Shell 
rather thin, oval, elliptical, swelled, nearly equilateral, broader be- 
hind, outside very smooth, and chesnut colour ; inside, bluish white. 
Length 4-5, diameter 3-5, axis 3-7 of the breadth. . 
Knob-hills streams, in east Kentucky.—Very small, lamellar tooth 
suboblique, thin. Perhaps a variety of U. lenigata. Sp. 9. 
G. TRUNCILLA. 
99 Sp. Unio perplexus. (Tr. perplexa, 1830.) Shell rather 
uboval, slightly swelled, only subtruncate ; rounded below, outside 
