60 NEW UNlONID.Ii OF THE 



slightly curved ; anterior cicatrices distinct, the smaller one being larger tlian usual; 

 posterior cicatrices continent; dorsal cicatrices placed on the plate and in the centre 

 of the cavity of the beaks ; cavity of the shell rather deep ; cavity of the beaks rather 

 shallow and subangular; nacre bluish white and very iridescent. 



Soft Parts. — Branchial litems very large, occupying that portion of the outer 

 branchias which is posterior to the abdominal sack. In the specimens under exami- 

 nation there are fifteen branchial ovisacks on each side, the larger ones being in the 

 middle, the others gradually diminishing towards the ends, the border is blackish. 

 Branchice large, the inner much the larger, rounded below, free* only at the point of 

 abdominal sack. Palpi very small, acutely angular at the point, free on the posterior 

 edges. Mantle thick and double along the edge, the color (brown) being deeper in the 

 fold on the border. Brarichial opening with rather large brownish papillae. Anal 

 ope7iin(/ with very small brownish papillse along the margin. Super-anal openinri large 

 and colored on the edges. Color of the mass whitish 



Remarhs. — This is a species nearly allied to modioliformis, (nobis,) from South 

 Carolina. It differs in being less inflated, less contracted anteriorly, and in having 

 broader and more numerous rays, as well as in having rather thicker teeth and thicker 

 nacre. The contraction in jwoc/zoZi/onni* is more towards the anterior margin. I have 

 seen no specimen of rutilans, which has not been very much rayed nearly over the 

 whole disk. The rays are usually broad on the umbonial slope. The figure is that of 

 a female. 



Unio errans. pi. 9 fig. 42. 



Testa Ijevi, oblonga, compressa, vald6 insequilaterali ; valvulis subcrassis ; natibus prominulis ; epidermide 

 tenebroso-fusca, obsolete radiatfi ; dentibus oardinalibus parvis, compressis ; lateralibus prmlongis, 

 lamellatis subrectisque ; margarita vel purpurea vel salmonis colore tincta et iridescente. 



Shell smooth, oblong, compressed, very inequilateral ; valves rather thick ; heaks a 

 little prominent ; epidermis dark brown, obscurely radiated ; cardinal teeth small, 

 compressed ; lateral teeth very long, lamellar and nearly straight ; nacre purple or 

 salmon and iridescent. 



Proc. Acad. Nat. Sci. 18.56, p. 262. 



Hah. — Tobesaufke Creek, near Macon, Georgia. Bishop Elliott. 



My cabinet and cabinet of Bishop Elliott. 

 Diam. -9, Length 1-5, Breadth 2-9 inches. 



Shell smooth, oblong, compressed, very inequilateral, rather flattened in the middle 

 towards the ba.se, rather truncate before and subbiangular behind ; substance of the 

 shell not very thick ; beaks a little prominent ; ligament rather long and somewhat 

 thick ; epidermis very dark brown, obscurely rayed, poHshed on the sides and striate 



* Another specimen from the same locality subsequently received, exhibits the same characters in the shell 

 and the soft parts, in every respect, except that the branchice are not free, and there is a little tint of color on 

 the margin of the branchial uterus. 



1 



