26 UE.SCRIPTIOKS 01- 



Eab. — River Macacou, Rio de Janeiro, Brazil, Prof. Diinker. New Granada, Mr. E. 

 Verreaux. 



My cabinet and cabinets of Prof. Diinker, Cassel, and Mr. Verreaux, Paris. 

 Diam. -7. Length ll, Breadth 2-2 inches. 



Shell folded, transverse, somewhat inflated, very inequilateral, obtusely angular 

 behind, with dorsal and basal margins nearly parallel ; substance of the shell rather 

 thin ; beaks a little prominent, with rather large diverging ribs reaching some distance 

 on the disk ; ligament rather long and thin ; epidermis blackish brown, very much 

 polished and rather regularly and transversely wrinkled, apparently without rays ; 

 umbonial slope rounded ; cardinal teeth long, compressed, double in the right and 

 single in the left valve ; lateral teeth very long, lamellar and straight ; the two inferior 

 anterior cicatrices confluent, the superior one distinct; posterior cicatrices confluent; 

 dorsal cicatrices placed in the cavity of the beaks ; cavity of the shell rather deep ; 

 cavity of the beaks very shallow and subangular ; nacre bluish white and very 

 iridescent. 



Remarlcs. — I owe the possession of this beautiful species to my friend Prof. Diinker, 

 of Cassel, to whom I dedicate it. Subsequently I procured a specimen from Mr. 

 Verreaux, of Paris. When Prof. Diinker presented me with the specimen, he was 

 under the impression that it was D'Orbigny's rhuocoica, but that is quite a distinct 

 species, being less transverse, of a lighter brown and with smaller and shorter costse at 

 the beaks. The costge of Dilnlcerianus extend, in the two specimens before me, so much 

 longer over the disk, and particularly near the umbonial slope, that it must be entitled 

 to be placed among the folded species. 



Unio nucleus, pi. 28, fig. 21. 



Testa plicata, quadrata, inflata, subsequilaterali, postice angulata; valvulis crassis; natibus prominentibus, 

 perplicatis ; epidermide virido fusca, miuutissimfe perstriata ; dentibus cardinalibus crassis brevibusque ; 

 lateralibus crassis brevibusque, in utroque valvulo duplicibus subcurvisque ; inargarita casraleo alba et 

 iridescente. 

 Shell plicate, quadrate, inflated, nearly equilateral, angular behind ; valves thick ; 

 beaks prominent, covered with folds ; epidermis greenish brown, filled with minute 

 strige ; cardinal teeth thick and short ; lateral teeth thick, short, double in both valves 

 and somewhat curved ; nacre bluish white and iridescent. 

 Proc. Acad. Nat. Sci. Vol. 8, p. 94. 



5a&.— Siam. S. R. House, M. D. 



My cabinet and cabinet of W. A. Haines, New York. 

 Diam. '3, Length -4, Breadth -6 inch. 



Shell folded, quadrate, inflated, nearly equilateral, angular behind ; subs'tance of 

 the shell thick, but shewing the undulations within ; beaks rather prominent, sub- 



