SPHAERODACTYLUS. 
INTRODUCTION. 
TuerE is scarcely a single Neotropical genus which 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 gradually accumulated. This 
series represents no less than thirty-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 courtesy which I have 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 peculiar 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 
1 It is interesting that the possession of this unique character is shared by the genus Aristelliger, 
which is also Antillean and not distantly related. 
