49 



Paludina decisa. — Shell subconic, olivaceous, truncated at 

 the apex ; whorls four, wrinkled across and banded with minute 

 distant striae.; terminal whorl 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 4 fiava vin'descens, non fasciata. Lister, 

 Condi, tab. 127, Jig. 27. 



The young shell resembles L. mhcarinata, 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 

 with 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. 



Grenus Unio. — Shell transverse ; with three deeply impressed 

 cicatrices ; hinge with a strong irregular tooth, and anterior lamel- 

 lifonn, 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 Mj/se, fi'om which they diifer in verj- 

 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, diiferent 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, 4 2 

 2 " " 4i 



2 " "2 



Plate 1, fig. 8. 

 Musculis brevoir, admodum crassus, ex interna parte subrosens. 



