UNITED STATES AXD NORTIIERX MEXICO. 13 



Unio Raeensis. pi. 52, fig. 150. 



Testa Irevi, oblonga, subiiiflata, ad latere subinipressa, posticc" tuniida et biangulata; valde innoquilaterali, 

 ad basim emarginata ; valvulis subcrassis; natibua prominulis; epidermide rufo-fusca, substriata, 

 obsolete radiata ; dentibus cardinalibus parvis, vald6 crenulatis; lateralibus praelongis curvisquc ; 

 raargarita purpurea et iridescente. 



Shell smooth, oblong, rather inflated, impressed on the sides, swollen and biangular 

 behind, very inequilateral, emarginate at the base; valves somewhat thick; beaks 

 slightly prominent; epidermis reddish brown, somewhat striate and oljscurely rayed ; 

 cardinal teeth small, very crenulate; lateral teeth very long and curved; nacre 

 purple and iridescent. 



Proc. Acad. Nat. Sci., 1859, p. 171. 



Hah. — Chattahoochee, near Columbus and Rae's Creek, Georgia. Bishop Elliott. 



My cabinet and cabinet of Bishop Elliott. 

 Diam. -8, Length 1-2, Breadth 23 inches. 



Shell smooth, oblong, rather inflated, impressed on the sides, swollen and biangular 

 behind, rather obliquely rounded before, very inequilateral, emarginate at the base ; 

 substance of the shell somewhat thick, very slightly thickened before; beaks slightly 

 prominent ; ligament rather long, thin and light brown ; epidermis reddish brown, 

 somewhat striate, obscurely rayed, with well defined and rather close lines of growth ; 

 umbouial slope much rai,sed, inflated and rounded; posterior slope slightly raised, 

 with obscure small rays and with an obscure raised line from the beak on each valve 

 to the posterior margin ; cardinal teeth small, slightly raised and very crenulate ; 

 lateral teeth veiy long, lamellar and curved ; anterior cicatrices distinct and well 

 impressed; posterior cicatrices confluent and but slightly impressed; dorsal cicatrices 

 small and placed under the plate, posterior to the cardinal teeth ; cavity of the shell 

 rather deep and wide; cavity of the beaks very shallow and rounded; nacre purple, 

 slightl}' tinted with salmon and iridescent. 



Soft Parts. — Brancldal uterus not charged, but ova were found in the ovarium. 

 Branchioi rather small, oblique behind and rounded before, inner ones very much the 

 larger, free nearly the whole length of abdominal sack. Palpi small, subtriangular, 

 united one-fourth down the posterior edges. Mantle thin, thickened on the posterior 

 edges. Branchial opening small, with a few, rather small, brownish papillae. Anal 

 opening large, with numerous, very small dark brown papilla;. Super-anal ojmiing 

 small, colored within and united below ; color of the mass whitish. 



Remarks. — Only two specimens were received from Bishop Elliott, the smaller one, 

 apparently half grown, was in alcohol. The larger one seems to be entirely adult 

 and is the one figured. In outline it is very near to Neusensis (nobis), but it is more 

 inflated, has smaller teeth and a much lighter colored epidermis. In the enlarged 

 umbouial slope and general form it is somewhat like denigratus (nobis), but differs in 



