SPHAERODACTYLUS. 



INTRODUCTION. 



There is scarcely a single Neotropical genus \Yhich has proved more baffling 

 to students than the one chosen for revision now. The species are often ex- 

 tremely small, adequate series of specimens are not frequently available, and as is 

 common in generalized, homogeneous groups, the characters available for specific 

 definition prove to be variable in the extreme. Thus while with the fresh 

 material in hand the reviewer has no great difficulty in separating the various 

 forms, yet when he comes to justify his conclusions by actually describing the 

 conditions observed, the task becomes one of most acute difficulty; while the 

 preparation of satisfactory keys for the determination of the species is an almost 

 hopeless task. I was led to attempt this revision solely by the fact that owing 

 to the long interest in West Indian exploration, which has centred in the M. C. Z. 

 a series of several hundred sphaerodactyls has gradual^ accumulated. This 

 series represents no less than thkty-one species of the thirty-five which are 

 recognized as valid including typical material of twenty species and fifteen types 

 of valid species. 



I acknowledge with deep gratitude the coiu-tesy which I ha\e received 

 from Drs. Leonhard Stejneger, G. A. Boulenger, Lars G. Andersson, A. G. 

 Ruthven, Mr. G. K. Noble, and Mr. H. W. Fowler, all of whom have aided my 

 studies. The quite satisfactory drawings are by Mr. E. N. Fischer, whose skill 

 is already well recognized. 



The sphaerodactyls form a compact group of Gekkonidae highly charac- 

 teristic of the Antillean subregion and the adjacent mainland. All the species, 

 except one, are found in countries bordered by the Caribbean Sea. This one is 

 the pecuhar species on Cocos Island off the Pacific coast of Costa Rica. I 

 noticed that three others from South America differed from all the rest in that 

 they lacked the supraorbital spine,' a character of great taxonomic importance. 

 Therefore, though they have been called Sphaerodactylus there seems good 



' It is interesting that the possession of this unique character is shared by the genus AristeUiger, 

 which is also Antillean and not distantly related. 



