A Contribution to our Knoiuledge of the Anatomy of Chamaeleons. 99 
not reach the jugal. In the several Cape species helonging to the 
pitmihcs group, the prosquamosal does not reach to the tip of the parietal, 
but is met by a descending lateral process of that bone, whilst anteriorly 
it forms a suture with the postfrontal, but does not reach the jugal. In 
this latter respect the pumilns condition resembles that in Varanus, whilst 
the dilepis condition is like that in Agama. According to W. K. Parker's 
figures, the prosquamosal of a juvenile C. vulgaris does not reach the 
jugal, whilst in the adult of that species, as in dilepis, it forms a fairly 
broad suture therewith. In Broohesia (and apparently also in Rham- 
pholeon) the prosquamosal is completely separated from the jugal. 
Assuming the accuracy of Parker's figure and statement concerning 
the young of G. vulgaris it would appear that the primitive condition 
is that of C. pumilns and Brookesia. 
The squamosal, though small, is quite distinct both in the dilepis 
and in the piimilus group, and indeed in all species of the large genus 
Ckamaeleon examined by us, being best developed in C. dilepis and alhes. 
In G. ventralis the outer surface of the squamosal occupies a hollow 
between the prosquamosal and the exoccipital, and by the growth of 
these two bones the squamosal is squeezed to the interior. In Bhampholeon 
it is said to be absent. In Brookesia the bone is exposed only to a very 
slight extent in external view, appearing at the base of the prosquamosal, 
and resting on the quadrate : if the prosquamosal be removed, the 
squamosal can be seen to extend upwards for a considerable distance. 
The presence of both prosquamosal and squamosal in a reptilian 
skull is generally considered the more primitive condition, yet Sphenodon 
has only one bone. In Sphenodon that bone is often stated to be the 
homologue of the mammalian squamosal, in which case if the inner bone 
of a Varanus skull is correctly homologized with the squamosal of 
mammals it would appear that the single bone found in Bhamp)holeon 
(or the larger one in Brookesia), though occupying precisely the same 
position relative to the other bones of the skull, is nevertheless not 
homologous with the single bone of Sphenodon. To us it would seem 
just as probable that the single element in Bhampholeon (one of the most 
primitive of Ehiptoglossa) and of Sphenodon are homologues ; from this it 
would follow that either this element in Sphenodon is a prosquamosal, 
or the outer element in Varanus and lizards in general is a true 
squamosal. 
We are not, however, in a position to determine this point, and we 
doubt if it ever will be possible to determine with certainty the lacertilian 
homologue of the single bone in sphenodon. The enlargement of the 
prosquamosal and the accompanying reduction of the squamosal is 
probably not due to the formation of the casque, as might perhaps have 
been suspected from consideration of G. quilensis or of G. vulgaris, 
