49 
Paludina decisa. — Shell subconic, olivaceous, truncated at 
the apex ; wborls four, wrinkled across and banded witli minute 
distant strim; terminal wborl very short; suture impressed and 
conspicuous ; aperture subovate, more than half of the length of 
the shell, entire ; within bluish white. Operculum coriaceous, 
elevated on the disk and concentrically striated. Length one inch ; 
breadth three-fourths. Plate 2, fig. 6. 
Cochlea virginiana e flava viridescens, non fasciata. Li&ter. 
Conch, tah. 27. 
The young shell resembles L. suhcarinata, but the whorls are des- 
titute of an elevated line, the suture is not so deeply impressed, 
and the aperture is narrower above. 
Animal with the foot larger, suddenly a little dilated each side 
before and truncate in front, widely ; foot livid, thickly maculated 
vath irregular orange spots, which are much smaller beneath ; head 
and tentacula spotted with orange ; eyes on a prominent angle, at 
the external base of the tentacula. 
I found the animal viviparous in October ; the young shell had 
then three complete whorls, which were spirally striated. 
Gienus Unio. — Shell transverse ; with three deeply impressed 
cicatrices ; hinge with a strong irregular tooth, and anterior lamel- 
liform, elongated one in one valve, inserted between two corres- 
ponding teeth and laminae of the other. 
Ohs. The shells of this genus inhabit fresh water ; they were 
placed by Linnaeus with the Myse, from which they differ in very 
essential particulars; as is obvious from the number, situation, and 
figure of the teeth, and the organization and habits of the included 
animal. 
Unio Crassus. — Shell varying in form and surface ; remarka- 
bly thick and ponderous ; epidermis horn-color, different shades of 
brown or black ; beaks carious, often much eroded, pure perlaceous, 
or silvery white, more prominent as the shell approaches an orbicu- 
lar form ; primary teeth, not very oblique. The dimensions of 
three specimens were as follows : 
Length, 3 inches; breadth, 
2 4J 
2 a a 2. 
Plate 1, fig. 8. 
Musculis hrevoir, admodum crassus, ex interna parte suhroseus, 
