208 DR. H, GADOW ON MEXICAN [June 6, 



shrubs at the edge of a forest, were quite green, but they soon 

 chano'ed to reddish yellow and ultimately assumed the normal 

 reddish colour. 



Of the 5 species of Leptodactylu,s, 3 are too little known, 

 L. tnicrotis from " Guanajuato " would be the only instance of the 

 occurrence of a Lej^todactylus on the plateau instead of in the 

 lowlands. Only two species have a wide distribution : L. alhilabris 

 of South Guerrero, Oaxaca, and of Yera Cruz, also Antillean ; 

 L. caliginosus from Paraguay northwards, in Mexico in the 

 Pacific Tierra Caliente as far as Mazatlan. 



Engystomatid^, with an obviously South- American centre of 

 dispersal ; not Antillean. The small genus Engystoma reaches 

 through Mexico into the South-eastern United States [E. usticm). 



Ranid^. — This family is essentially Palseo-tropical. Scarcely 

 more than a dozen species, all belonging to Rana, occur in North 

 America, only 6 in Mexico, and fewer still further south, in 

 the north-western portion of South America. There, however, 

 the Ranida3 have found a new congenial home, which has stimulated 

 them into the development of 5 new genera, with about one dozen 

 species, all arboi"eal, besides Bendrobates. The Ranidee have not 

 found their way into the Antilles. 



Of the six Mexican species, B. forreri is restricted to the district 

 between Durango and Mazatlan ; R. 2}^<'Stulosa to same district 

 and Western Jalisco ; R. omiltemana to Guerrero mountains : 

 these three are peculiar to Mexico. R. halecina is the common 

 river-frog of the covmtry, both in the hot parts and on the plateau, 

 extending from the United States through the whole of Mexico 

 down to Costa Rica. R pahnij^es ranges from southern tropical 

 Mexico to South America. Lastly, R. montezicmce, the largest of 

 all, is a lake-dweller, e. g. lakes of Jalisco, near Mexico City, 

 Tehuantepec, extending south into Tabasco and Guatemala. 



Resume of the Distrihution of Mexican Aiiura. 



We can easily distinguish between northern and southern 

 immigrants. 



1. Northern, decidedly of Nearctic origin. Scaphioptis, scarcely 

 reaching the Isthmus of Tehuantepec; and a few Rana, all water- 

 frogs. Both genera are comparatively recent immigrants, non- 

 Antillean, although Rana extends through and beyond Central 

 America. 



2. Southern, of obvious South-American origin. — a. With 

 related, or identical, species in the Gi^eater Antilles. Gysti- 

 gnathidce, not reaching the United States. Hylidce and Biofonidw, 

 each, especially the Hylidte, with genera peculiar to Mexico, 

 indicating ancient residence. — h. ISTon- Antillean, a few Engysto- 

 matince, scattered throvigh Mexico. 



