A MONOGRAPH OF THE AMERICAN FROGS OF THE 



GENUS RANA. 



By G. a. Boulenger, LL.D., D.Sc, F.R.S., &c. 



Presented by Thomas Barbour. Received December 1, 1919. 



I HAVE lately been able to make a thorough revision of the numer- 

 ous species, about 195, constituting the genus Rana in the broad sense 

 in which I take it.^ 



For purposes of convenience, and also in order to facilitate its pub- 

 lication, I have divided the work into four parts, based on the geo- 

 graphical distribution. The first part, dealing with the South Asian, 

 Papuan, Malanasian and Australian species, will be published, thanks 

 to the kind interest of Dr. Annandale, in the Records of the Indian 

 Museum, and is nearly entirely printed. The part dealing with Amer- 

 ica, comprising a comparatively small number of species, is now 

 offered for publication. 



The latest comprehensive accounts of the North American species 

 are contained in the works of Cope, Batrachia of North America, 

 (Bull. U. S. Nat. Mus. No. 34, 1889), and of Miss Dickerson, whose 

 Frog Book (1906) is so excellently illustrated and swarms with inter- 

 esting information on the life histories. The Central American 

 species have been dealt with by Giinther in the Biologia Centrali- 

 Americana (1900). 



From a systematic point of view, the descriptions in these works 

 are not so precise and comparative as I should Avish, and do not convey 

 that information on individual variations in the proportions that are 

 of essential importance in a group in which the absence of scales 

 deprives us of so many characters which facilitate the identification 

 and study of reptiles. That is why I have thought it desirable to 

 prepare tables of measurements of a large number of individuals to 

 accompany the descriptions, drawn up on a strictly comparative 

 system and taking into consideration all departures from the normal. 



These descriptions and tables will enable the student to form a 

 correct idea of the material in the British Museum, material Avhich, 

 though less exhaustive than that in some institutions in the United 

 States, is j^et of great extent, especially as concerns IVIexico and 

 Central America. It has been recently increased through the gener- 



1 Cf. Bull. Soc. Zool. France (1918), p. 111. 



