THE REPTILES OF THE GALAPAGOS ISLANDS. 75 



deuce they became separated, and that the modern forms 

 of life, with exception, perhaps, of one or a few of recent 

 introduction, are simply the descendants of continental 

 forms established in their present localities before the con- 

 necting lowlands disappeared in the ocean. In both theo- 

 ries, isolation and differences of circumstances were the 

 important factors in differentiation ; and the closeness of 

 existing relationships may be cited in favor of each of the 

 hypotheses. 



The portion of the collection submitted to me for ex- 

 amination suffices for special determinations but is insuffi- 

 cient for purposes of generalization. It indicates that a 

 most important contribution to the scientific history of 

 the region might be made by one who is able to gather 

 from each of the islands series large enough to supply the 

 now-lacking means for comparisons. His most extensive 

 series, that of Tropidurus, and the tortoises have already 

 been studied by the Doctor himself. Among those identi- 

 fied in this paper his collection has added one genus, 

 Gonatodes, and two new species, Gonatodes collaris and 

 Phyllodaclylus Baurii, to the list of those reported from 

 these localities. 



One of the most interesting specimens in the collection 

 is a small Conolophus from Barringtou. It is important 

 because of the opportunity it affords for a description of 

 the young, and because of the light it throws on the deri- 

 vation of the genus. Its resemblance to forms of Enya- 

 lioides is so great that if larger individuals were unknown 

 we should place it in that genus by the side of E. laticeps, 

 as a closely allied species. A comparison of this speci- 

 men with others of species of Enyalioides makes it very 

 evident that Conolophus was derived from one of their 

 immediate ancestors, the nearest, perhaps, that of E. lati- 

 ceps. Conolophus and Amblyrhynchus have close anatomi- 



