230 
Transactions of the Royal Society of South Africa. 
stand when we started. The following synopsis has been drawn up by the 
senior author, from the material then available to him in the British 
Museum, as a basis for discussion and criticism on the part of his junior, 
who, though less favourably situated to deal with the historical aspect of 
the question, enjoyed the superiority of having access to much larger 
collections,* and was thus in a better position to judge of the constancy 
of the characters selected for the distinction of species and varieties. It 
will be seen further on how far this first tentative scheme of classification 
reflected the true state of things in Nature. 
Synopsis of the Species (1916). 
I. Dursu-lateral scales Avith the keels pointing obliquely inwards (towards the verte- 
bral line) ; 70 to 115 scales round middle of body. 
A. Upper parts very rough Avitli enlarged spinose scales ; a low crest or serration 
along the middle of the back, at least indicated by a regular series of strongly 
keeled scales (exceptionally interrupted) ; scales on upper surface of tibia 
unequal in size ; fifth toe only exceptionally extending as far as first ; tail not 
compressed, not crested, as a rule shorter than head and body in females. 
Diameter of ear-opening much less than cleft of closed eye ; third 
toe longer than fourth ; ventral scales more or less keeled, usually 
strongly mucronate A. liispida, L. 
Diameter of ear-opening much less than cleft of closed eye ; third 
and fourth toes equal, or fourth slightly the longer ; ventral scales 
smooth or feebly keeled . . . . . . .A. hrachyura, Blgr. 
Diameter of ear-opening equal to or a little less than cleft of closed 
eye ; third toe longest (exceptionally third and fourth equal) ; 
ventral scales smooth or feebly keeled . . . . A. distanti, Blgr. 
B. Upper parts not so rough, the enlarged scales forming- more or less regular 
longitudinal series ; a low crest or serration on the middle of the back, as in 
the preceding ; scales on upper surface of tibia equal or nearly so ; toes more 
slender, fifth extending as far as first, third and fourth equal or either slightly 
the longer; tail not compressed, not crested, longer than head and body in 
both sexes. 
Head a little longer than broad ; ventral scales more or less 
strongly keeled and mucronate ...... A. armaia, Peters. 
Head as long as broad ; ventral scales smooth or faintly keeled 
A aculeata, Merr. 
c. Enlarged dorsal scales few or very irregularly scattered ; scales on upper 
^urface of tibia equal ; fifth toe extending as far as first, third extending- 
* The collection in the British Museum contained only 37 specimens in 1885 ; in 
1916, when Ave started Avork in collaboration, the number had risen to 232. In 
addition to these Ave had at our disposal the collections of the various South African 
museums, making up a very extensive series. It may be mentioned here that Ave 
have tabulated only those specimens which Ave considered sexually mature. These 
numbered some 757, but this number by no means represents the vast amount of 
material that Ave have examined. We beg to express our grateful thanks to the 
Directors of the A^arious museums for their kindness in putting the material under 
their charge at our disposal. 
