40 WILLIAM K. GREGORY 
scription of the skulls of Diademodon and other Cynodonts, states 
that there is no suture between the epipterygoid, or temporal 
wing of the alisphenoid, and the pterygoid; that the whole ptery- — 
goid plus epipterygoid corresponds and is homologous with the 
mammalian alisphenoid in all its relations to surrounding ele- 
ments and to nerve exits. The ‘pterygoid wings of the ali- 
sphenoid” in mammals together with the basal portions of the 
alisphenoids are therefore homologous with the pterygoids of 
reptiles. The true mammalian pterygoids, which are slips of 
bone on the inner side of the pterygo-alisphenoids are homologized 
by Watson with the ectopterygoids of Cynodonts, as first sug- 
gested by Seeley. 
These conclusions are entirely consistent with the facts set 
forth in the preceding pages and offer a very satisfactory explana- 
tion of the fate of the ectopterygoids and pterygoids in the Cyno- 
dont-like ancestors of the mammals. 
Dr. R. Broom (’12) in working out a natural brain cast of Di- 
eynodon finds that the fenestra ovalis of the internal ear is filled 
by the inner end of the rod-like bone which he formerly called 
tympanic but which he now recognizes as stapes. The outer 
end of the stapes abuts against the quadrate. The quadrate 
therefore corresponds in position with the mammalian incus and 
Broom accordingly accepts the homologies of the Theriodont 
quadrate and articular which were suggested by the present 
‘writer in 1910, when applying Reichert’s theory to the Therio- 
dontia. 
The writer’s application of Reichert’s theory to the mammal- 
like reptiles is contested by Dr. Hugo Fuchs (12). His most 
important point, the ‘fixed’ condition of the quadrate in Cyno- 
donts has been dealt with above (pp. 27, 36). The ‘caudal 
displacement of the quadrate’”’ in Monotremes has not removed 
the quadrate very far behind the glenoid region of the squamosal. 
His views of the homology and relations of the squamosal and of 
the epiphysial articular cartilage of the mandible have, it seems, 
already been answered satisfactorily by Gaupp. 
