oP, WILLIAM K. GREGORY 
matters, will realize that Gaupp has developed a perfectly con- 
sistent body of doctrines, resting upon many independent lines 
of evidence and offering a highly probable explanation of the 
two-fold problem of the lower jaw and of the auditory ossicles. 
It seems truly remarkable that these elaborate conclusions, 
developed with practically no aid from palaeontological evidence, 
should now be found to be entirely consistent with it. ‘Neon- 
tologists,’ as a rule, have been so busy gathering and sifting the 
intricate facts furnished by recent forms, they have devoted so 
much energy to the elaborate embryological technique, they have 
heard so much and so often about the fragmentary nature of 
palaeontological evidence, that until very recently they have 
failed to realize the critical importance in the problems under 
consideration of the Theriodont reptiles of the Permian and 
Triassic. Palaeontologists, on the other hand, with the passing 
of Owen, Cope and Baur, have for the most part ceased to con- 
tribute to neontological research on the vertebrate skull and 
with few exceptions, have taken little or no part in discussing 
the origin of the mammalian lower jaw and auditory ossicles. 
The first effective application of palaeontological evidence to 
the lower jaw problem was made by Dr. R. Broom (’04) who 
pointed out the marked approach toward mammalian conditions 
exhibited by the Theriodonts and suggested that the ascending 
ramus of the dentary grew backward until the condylar region 
came into contact with the squamosal. The next year Gaupp 
(05) without reference to the Theriodonts, suggested the same 
view, but his explanation of the manner in which the new joint 
arose was based largely on the conditions in the lizard, and these 
conditions as elsewhere shown (Gregory ’10) are essentially un- 
favorable to the origin of the mammalian type of articulation. 
Gaupp (11, pp. 619-623) now accepts the lower jaw of Cynogna- 
thus (fig. 16) as virtually offering the fulfilment of the hypotheti- 
cal conditions for the jaw of the ancestral mammal. 
