276 NEW UNIONID^, MELANID^, ETC., 



super-anal opening. Color of the mass pale salmon. The foot has very much the 

 appearance of that of Mycetopus, described and figured by D'Orbigny in his Voy . Am. 

 Merid., but the muscular fibre in the single specimen before me is very much con- 

 tracted by the alcohol. 



Hah. — South America, Don Patricio M. Paz. 



My cabinet and cabinet of Don P. M. Paz. 



Bemarhs. — A single specimen with the soft parts was received. The outer or hard 

 parts measure 4 J inches in width. Specimens which I have had a long time in my 

 cabinet from Central America are three inches wide. That figured in Spix's Test. 

 Braz. measures 1'6 inches, of course quite a young specimen. This has created some 

 confusion, and induced Dr. "Wagner to consider that Anodonta siUqiiosa, Spix, and 

 An. pygmcea, Spix, were the same. But I am now satisfied that they are distinct 

 species, and both belong to D'Orbigny's genus Mycetopus, which he describes as perfo- 

 rating the earth like Pholades, below the water, and which corresponds with the 

 habits of our Margaritana dekiscens, Say, = M. oriens, Lea, being rarely found except 

 in such holes. 



It is to be regretted that the only specimen received should have proved to be a 

 male, as the form of the branchial uterus, as well as that of the embryonic shell, 

 would have been of great interest. M. D'Orbigny does not seem to have observed 

 these forms, as he does not mention them in his description o£ Mycetopus, which does 

 not differ much from Uuio. 



Unio Jewettii. PL 37, fig. 89. 



Testa Isevi, oblonga, subinflata, valde intequilaterali, postice obtuse angulata, antice rotundata ; 

 valvulis subtenuibus; natibus prominulis, ad apices concentrico-undulatis ; ei^dermide fusca; 

 dentibus cardinalibus parvis, obliquis, compressis ; lateralibus priielongis lamellatisque ; margarita 

 alba et iridescente. 



Shell smooth, oblong, rather inflated, very inequilateral, obtusely angular behind, 

 rounded before ; valves rather thin ; beaks a little prominent, concentrically 

 undulate at the tips ; epidermis brownish ; cardinal teeth small, oblique and com- 

 pressed ; lateral teeth very long and lamellar ; nacre white and iridescent. 

 Proc. Acad. Nat. Sci. 1867, p. 81. 



Bab. — Sink of Noonan's Lake, Florida, Col. E. Jewett. 



My cabinet and cabinets of Col. Jewett and Dr. Lewis. 

 Diam. "7, Length 1-1, Breadth 1-9 inch. 



Shell smooth, oblong, somewhat inflated, inequilateral, obtusely angular behind, 

 rounded before ; substance of the shell rather thin ; beaks a little prominent, con- 

 centrically undulate at the tips ; ligament long and thin ; epidermis brownish, 



