1909.] NATURAL SCIENCES OF PHILADELPHIA. 519 



MELANIID.E OF THE PANUCO RIVER SYSTEM, MEXICO. 

 BY H. A. PILSBRY and A. A. HINKLEY. 



The Pachycheili of the Panuco River system are all, so far as known, 

 special to that drainage. * These waters are remarkably rich in fine 

 species, which though not so large as some from Central America, are 

 more varied in shape and sculpture. In a few species the spire is so 

 short that the shell has a globular or oval shape, like Anculosa or 

 Paludomus ; yet in the structure of the aperture and operculum these 

 aberrant forms agree with more normal species of the same region. 

 One species, P. pleurotoma, has a Pleurotomoid sinus in the outer lip, 

 somewhat like that of P. dalli Pils., but situated farther up. 



The whole group of the Panuco drainage differs from the southern 

 forms of Pachycheilus in the weakness or absence of the regular and 

 close microscopic spiral striation characteristic of the typical species. 



The shells are generally abundant. Of most of the forms several 

 hundred shells at least of each species have been examined. All were 

 collected by Mr. Hinkley during the past winter. The descriptions 

 are the joint work of both authors. The figures are natural size. 

 Cotypes of the new forms are in the collections of the Academy of 

 Natural Sciences of Philadelphia and of Mr. Hinkley. 



Since many of the localities mentioned herein are not indicated 

 on maps available in this country, we give here a sketch of the lower 

 portion of the Panuco River System. 2 



1 It is possible that P. pluristriatus is an exception, but the record of that 

 species from a West Mexican lake seems improbable. 



2 Localities where mollusca were collected during the whiter of 1908 and 1909 

 are marked on the map with numerals. These numbered stations are as follows: 



No. 1. LaBarra. 



" 2. Tampico. 



" 3. Cave from which the Choy River issues. 



" 4. Taninul, flag station for Hot Spring. 



" 5. Hot Spring. 



" 6. Catamas Lake. 



" 7. Pujal Lake. 



" 8. El Abra. 



" 9. Valles Station. 



" 10. Valles. 



" 11. Small falls of the Valles River. 



" 12. Ranch of Mr. Willis. 



" 13. Chaimi Creek. 



" 14. Pujal, Pujal ferry and ford. 



" 15. Ford or ferry of the Coy River. 



" 16. Alligator Lake. 



" 17. First rill in the mountains south of Valles. 



