1903.] NATURAL SCIENCES OF PHILADELPHIA. 761 



MEXICAN LAND AND FRESHWATER MOLLUSKS. 

 BY HENRY A. PILSBRY. 



The following report is based chiefly upon material collected by Mr. 

 S. N. Rhoads during two expeditions to Mexico; the first in February, 

 March and April, 1899, the second undertaken early in 1893, and un- 

 fortunately cut short by his recall to Philadelphia after only a few 

 days in the field. Occasion has been taken to include sundry notes 

 upon and descriptions of new Mexican and Central American mollusks 

 in the collection of the Academy, worked up in the course of study 

 upon Mr. Rhoads' collection; the whole being supplemental to the 

 great works upon this fauna of Fischer and^ Crosse, E. von IMartens 

 and H. Strebel.^ 



The species of greatest interest in Mr. Rhoads' collection is that I 

 have elsewhere described as Metostracon mima, an extraordinary slug- 

 like snail, which contributes not only a genus new to Mexico, but a 

 totally new line of differentiation in the family Helicidce. 



From the faunistic standpoint, the collections made at \'ictoria 

 in Tamaulipas, and at ^lonterey and the adjacent mining village of 

 Diente in Nuevo Leon, are of great importance, confirming the north- 

 ward extension of the Neotropical region in east Mexico, already 

 mapped on the evidence of the birds of that district. The localities 

 mentioned are sufficiently alike in their faunse to be considered 

 together. In a total of 46 species. 



Fifteen arc identical with characteristic species of Vera Cruz Prov- 

 ince; 



Three are identical with species of the States of Mexico, Jalisco, etc. ; 



Ten are identical with species of Texas 



(Five of the above occur from Vera Cruz to Texas); 



Twenty are species special to Nuevo Leon and Tamaulipas. but 

 belonging to Vera Cruzian genera or smaller groups ; 



Three are species special to Nuevo Leon and TamauliiDas, but 

 belonging to groups ranging from YersL Cruz to Texas. 



^ As the literature has been fully cited by these authors, I have thought the 

 insertion of references to be needless, except in dealing with new species described 

 in my previous paper on Mr. Rhoads' collection, and in a few other cases inade- 

 quately treated in the larger works, or omitted therefrom. 



