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A EEVISION OF THE SOUTH AFRICAN AGAMAS ALLIED TO 
AGAMA HISPIDA AND A. ATBA. 
By Gt. a. Boulenger and J. H. Power. 
(With three Text-figures.) 
Introduction. 
No group of South African reptiles stood more in need of revision 
than the forms of the genus Agama that cluster round A. hispida and 
A. atra. This has been felt not only by us but by all whose task it has 
been to name specimens. The account in the British Museum Catalogue of 
Lizards, based on a very small series of specimens, has long ceased to fulfil 
its purpose, and the senior author had on various occasions endeavoured 
to improve the unsatisfactory state of things, but with little success, until 
we decided to join forces, in order, with the help of a very large material, 
to arrive at conclusions which would better stand the test of time. 
If we have not succeeded in drawing up definitions which will in every 
case enable the student to determine without hesitation any isolated example 
that may fall into his hands — although we hope and trust such failures will 
be rare — we feel sure this is not due to any want of care on our part, but to 
the state of things in Nature, which precludes such rigid diagnoses as those 
less versed in the difficulties of systematics expect to find in the writings on 
which they rely to guide them. It must have occurred to any one of a 
critical turn of mind, on referring to works of descriptive zoology or botany, 
that even the best descriptions of the commonest species, when put to the 
test of a very large material, rarely cover the whole range of individual 
variation, exceptional deviations from the normal having usually been passed 
over, and it is clear that the precision of the definitions stands at an inverse 
ratio to the number of specimens conscientiously examined by the authors. 
This fault we have endeavoured by every means to avoid, and the result of 
our attempts from the standpoint of diagnostic rigidity has suffered in 
consequence. But we must rejoice rather than lament over these difiiculties 
if they bring us nearer to truth. At any rate the work we have undertaken 
has been for us another lesson in the theory of evolution, and we recommend 
similar investigations to those who might still entertain doubts as to the 
derivation of species. 
Before proceeding with the exposition of our work and summing up its 
results, it may be of retrospective interest to show how matters appeared to 
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