532 PROCEEDINGS OF THE ACADEMY OF [NOV. 



UNIONIDJE OF THE PANUCO RIVER SYSTEM, MEXICO. 

 BY HENRY A. PILSBRY. 



The extensive river system emptying by the Panuco River into the 

 Gulf of Mexico at Tampico has a rich mollusk fauna, in which tire 

 Melaniidce and Unionidce are particularly well developed. A few of 

 the mussels were collected by Dr. Blanding many years ago and 

 described by Dr. Isaac Lea. Many more were taken by Mr. A. A. 

 Hinkley in January and February of the present year. All of the 

 species known from the Panuco drainage are included in the following 

 list. The localities mentioned may be found on the map, p. 520. 



Only four Panuco species are now known to extend southward into 

 the rivers of the neighborhood of Vera Cruz. There is more affinity 

 with the fauna of the Rio Salado. 



The generic relationships of eastern Mexican Unionidce are very 

 uncertain, since Simpson, in his great systematic work, knew the 

 soft parts of very few Mexican forms, and there are no definite generic 

 characters in the shells alone distinguishing the genera Unio, Nephro- 

 naias and Lampsilis. Some species which have been referred to the 

 two former genera seem to me to belong to Lampsilis. Under these 

 circumstances, it will be understood that the generic references herein 

 are made with reserve, and subject to revision by those who may study 

 these mussels in the flesh. 



Quadrula nickliniana (Lea). 



Unio n. Lea, Obs., I, 140; III, 72. 



Moctezuma River (Dr. Blanding). This large and handsome 



plicate species was not found by Mr. Hinkley. 



Quadrula semigranosa v. d. Busch. 



Unio semigranosus v. d. Busch, in Philippi, Abbild., I, p. 19, pi. 1, figs. 1-3. 

 Martens, Biologia, p. 493, pi. 30, figs. 1-4. 



Rio Panuco at Tampico, type loc. It has not been found by Mr. 

 Hinkley. 



My record of this species from Rio Tuliga in Tabasco, copied into 

 the Biologia by Prof, von Martens, was erroneous, the specimen from 

 that place being U. corium Sowb. and not semigranosus. This leaves 

 only the Panuco locality on record for the species, though related 



