324 NEW UNIONIDJE MELANIDvE, ETC., 



substance of the shell rather thick, somewhat thicker before ; beaks somewhat 

 prominent ; ligament rather short and thin ; epidermis dark brown, without rays ; 

 umbonial slope raised and rounded ; posterior slope wide and cordate ; cardinal teeth 

 compressed, oblique and very much crenulate, double in the right and disposed to be 

 treble in the left valve ; lateral teeth long, lamellar and corrugate ; anterior cicatrices 

 confluent, rather small and well impressed ; posterior cicatrices confluent and 

 slightly impressed ; dorsal cicatrices placed nearly, in the centre of the cavity of 

 the beaks ; cavity of the shell very deep and rounded ; cavity of the beaks deep 

 and rounded ; nacre silver-white. 



Remarlcs. — A single specimen, which was found among several of U. corrugata, 

 Lam., in the collection of the Academy of Natural Sciences. I have little doubt but 

 that it is a native of some of the rivers of South America. The beaks are very much 

 eroded. If they were perfect in the specimen their character would, I think, prove 

 the truth of this suggestion. The character of the cardinal teeth is similar to some 

 of the South American species. In the left valve it is treble, the anterior division 

 being very small, the middle one the largest. In the right valve the cardinal tooth 

 is double. The anterior cicatrices are so confluent as to show no disposition to be 

 separated. There is no appearance of this specimen ever having had rays, but it is 

 very far from being a perfect individual, and young and perfect ones may be rayed. 



Anodonta Napoensis. pi. 53, fig. 137, 



Testa Ixvi, oblongo-elliptica, subcompressa, valde injequilaterali, antice et postice rotundata; 

 valvulis subcrassis ; natibus prominulis; epidermide tenebroso-fusca, encarpiformi, flexuosa, 

 obsolete radiata ; margarita pallido-viridi, non iridescente. 



Shell smooth, oblong-elliptical, rather compressed, very inequilateral, rounded 

 before and behind ; valves rather thick; beaks a little prominent ; epidermis dark 

 brown, festooned, flexuous, obscurely radiate ; nacre pale green and not iridescent. 

 Proc. Acad. Nat. Sci. 1868, p. 162. 



Eab. — River Napo, Equador, South America, Prof Orton. 



My cabinet and cabinet of the Smithsonian Institution. 

 Diam. -7, Length 1-3, Breadth 2-4 inches. 



Shell smooth, oblong-elliptical, somewhat compressed, very inequilateral, rounded 

 before and behind; substance of the shell rather thick; beaks a little prominent; 

 ligament long, rather thick and dark; epidermis dark brown, festooned, flexuous, 

 obscurely radiate; umbonial slope rounded, with an elevated line from the beaks to 

 posterior margin; posterior slope slightly raised into a carina; anterior cicatrices 

 distinct, the larger one being very large and well impressed, the smaller one being 

 very small and not much impressed ; posterior cicatrices confluent, large and slightly 



