170 Transactions of the South African Philosophical Society. 
scription is fuller and more accurate than that of the earlier authors, 
we are still left in a state of much uncertainty on a number of points 
on which it is of great importance for the morphologist to have light. 
While engaged in the study of the comparative anatomy of Jacob- 
son’s Organ I was led to the conclusion that the lacertilian so called 
‘““vomer’’ is not the homologue of the mammalian vomer, but of 
the ‘“‘dumb-bell-shaped bone’’ in Ornithorhynchus and of the pala- 
tine process of the premaxillary in the higher mammals, For this 
element which is usually anchylosed with the premaxillary as its 
palatine process, but which remains distinct throughout life in Orni- 
thorhynchus, and in the little cave bat, Muuopterus schreibersi, I 
proposed the name of Prevomer.* To find further evidence in 
support of my position I naturally turned to the Theromorous 
reptiles as showing affinities with both the lizards and mammals. 
The examination of the beautiful skulls of Gomphognathus discovered 
by Seeley revealed that not only is there a well-developed true vomer, 
but that anteriorly are a pair of prevomers, situated exactly as are the 
palatine processes in the higher mammals but apparently quite dis- 
tinct from the premaxillary. t 
In the Anomodont skull the great development of the premaxillary 
renders the examination of the vomerine region difficult, and I found 
it impossible to get very satisfactory results from the British Museum 
specimens, though it soon became quite manifest that the median 
ridge on the posterior part of the hard palate which has been 
regarded by all previous writers, so far as I am aware, as the 
vomer, could not be the true vomer which undoubtedly is situated 
in the angle between the two anterior branches of the pterygoids. 
Since returning to South Africa I have come across a number of 
specimens, the examination of which has enabled me to settle 
definitely almost all the details of the anatomy of the palate. 
In Dicynodon and its near ally Oudenodon there is a well-developed 
bony roof to at least the anterior half of the mouth. On the anterior 
part of this bony roof or hard palate are two parallel longitudinal 
ridges, and in the posterior part is a well-developed median ridge. 
The structure of this hard palate has been a matter of some diffe- 
rence of opinion, as in the majority of the British Museum specimens 
the sutures are very indistinct. But while opinions have varied as 
to the extent of the premaxillary and maxillary elements, there has 
been a general agreement in regarding the median ridge as the vomer. 
* R. Broom, ‘‘ On the Homology of the Palatine Process of the Mammalian 
Premaxillary,’’ Proc. Linn. Soc. N.S.W., 1895, p. 555. 
+ R. Broom, ‘‘ On the Occurrence of an apparently distinct Prevomer in Gom- 
phognathus,” Journ, Anat. and Phys., vol. xxxi., p. 277, 
