South African Agcnnas allied to Agama hisphla and A. atra. 235 
question are not strictly geographical forms, and as from the fact that the 
characters on which the varieties are based are not constant, it will be 
optional to use the varietal name when it is required for the purpose of 
greater precision, or to drop it when the intermingling of forms is so 
complete as to render the distinction impracticable and hence worse than 
useless. And so we have dealt with the variation of Agama hispida in the 
wide sense, this lizard affording an excellent example of what we understand 
by the term " variety " as opposed to " species,'' and also of the difficulties 
with which the systematist is confronted in the case of polymorphic species. 
There is also the question to consider whether the different varieties 
when they meet in one district do not cross, and thus give rise to individuals 
which further add to the perplexity of the student. It is, indeed, highly 
probable that such hybrids, or rather mongrels, do occur in the Agamas, 
but we have no means of satisfying ourselves that they are such, and it 
would be unscientific to get over the difficulties l)y suggestions which do 
not rest on any observed fact. 
After long study, extending over three years, and embracing a very 
lai-ge material, we have agreed to divide the group of Agamas of which 
we undertook the revision into three species only : A. hispida, L., A. anchietae, 
Bocage, and A. atra, Daud., each of which includes a number of forms 
which cannot be defined with sufficient precision to justif y specific rank, and 
which we therefore call varieties. 
Synopsis of the Species. 
I. Terminal dorsal scale on the third or fourth toe not, or hnt little, 
longer than the penultimate ; dorso-lateral scales with the keels 
pointing obliquely inwards (towards the vertebral line) . 1. A. hispida, L. 
II. Terminal dorsal scale on the third or foiu^th toe much longer than the 
penultimate ; dorso-lateral scales with the keels j^ointing obliquely 
inwards . . . . . . . . . 2. A. anchietae, Bocage 
III. Terminal dorsal scale on the third or fourth toe much longer tlian 
tlie penultimate ; dorso-lateral scales with the keels pointing 
obliquely outwards 3. ^. atra, Daud. 
It will be noticed that the characters on which the definition of the 
species now rests are just such as have entirely escaped attention on the 
part of previous writers. 
A. hispida. — Five forms:/, typica, vars. armata. Peters, acnleata, Merr , 
distanti, Blgr., brachyiira, Blgr. 
A. a7ichietae.— Three forms: /. typica, var. methneni, Blgr. & Power, 
var. n. hnoheli, Blgr. & Power. 
A. atra. — Three forms: f. typica, yhy. holtihi, Bocage, var. rudis,'B\gr. 
ik Power. 
After each of these fonns had been described from the limited material 
