Garman.] 404 [June 21, 



A consequence of the similarity of climatic conditions in all its 

 parts and of the absence of obstructions is, that species have been 

 able to spread themselves over enormous extents of territory in the 

 torrid region, affected little by variation. 



Some idea of the condition of these orders in this and the eastern 

 districts may be obtained from the following instances, in which each 

 is represented by one of its most widely distributed and also by one 

 of its more restricted species. 



One of the most common reptiles in the torrid and eastern sections 

 is Iguana tuberculata Laur. Its range extends from Mexico to south- 

 ern Brazil, and — if we accept as valid the closely allied species 

 7. rliinolopha Wiegm., which occurs with it in Central America — it 

 nowhere, according to collections from upwards of twenty localities, 

 acquires differences enough to characterize a variety or to enable 

 the student, even approximately, to determine the locality from the 

 specimen. 



We are able to indicate from the specimens a range for Telus ni~ 

 gropunctatus Spix over the torrid section from Cape St. Roque and 

 Villa Bella to the Darien extremity of the Isthmus, not including 

 Ecuador. The variations shown by the most distant localities are 

 comparatively slight. In squamation they are similar throughout. 

 Specimens from the Gulf of Darien have the colors less mixed, the 

 yellow brighter and the brown darker; from Ceara have less yellow, 

 more olive, and greater confusion of markings; and from Villa Bella 

 have lighter colors generally, and a reddish tint — as figured by Spix. 

 In passing from one locality to another the changes are so gradual 

 that the separation of the species into groups of any value to the 

 student is next to impossible. In the eastern section this species is 

 displaced by Teius teguixin Linne. 



Among batrachians, Cystignathus ocellatus (L.) Tsch. has a range 

 which covers and exceeds that of Iguana. Its representatives in the 

 eastern section form a variety marked by colors and a somewhat 

 larger size. 



Bufo agua\j?itv. inhabits the entire torrid section; on the head 

 waters of the Tocantins a variety is characterized by smaller size 

 and colors; in the eastern section it is displaced by another species, 

 B. ictericus Spix. 



Other instances illustrating the community of species between the 

 Isthmus and the Amazon basin are enumerated below. It is not only 

 the larger and stronger that are common; the natural barriers seem 

 to have proved equally ineffectual against some of the species most 



