10 WILLIAM K. GREGORY 
sphenoids, are external to the carotid canals and posterior to the 
pterygoids. 
These comparisons, summarized in the following table, offer 
strong evidence for the view that the bones usually called ali- 
sphenoids in the Dinosaurs and crocodiles are rightly so named. 
If, however, the large temporal wing-bones of the braincase 
in crocodiles and Dinosaurs are alisphenoids where are the true 
orbitosphenoids? In the crocodile Parker (’83) sought the orbi- 
tosphenoids in the persistently cartilaginous lateral wings of the 
chondrocranium, lying above the presphenoid, behind the eth- 
moids, below the frontals and in front of the foramina for the 
optic nerves. These topographic relations are exactly similar to 
those of the orbitosphenoids of mammals, the chief difference 
being that in mammals, the orbitosphenoids are osseous. In 
the Cynodonts the region in front of the alisphenoids remained 
unossified (Broom). | 
TABLE 1 
Topographic resemblances between the ‘alisphenoids’ of crocodiles, dinosaurs, 
cynodonts and mammals 
ALISPHE- ALISPHE- ALISPHE- ALISPHE=- 
NOIDS OF NOIDS OF NOIDS OF NOIDS OF 
MAMMALS |CYNODONTS) CROCODILES} DINOSAURS 
Lateral to becicnhenoids and pitatary | 
HOSS yet as o's o colo bad COREE ren ncts co tie ie X x x x 
ADGETYOT Os PROCS. a3: ..0.%s2 <3. eee oe ee x xX xX x 
Inferior chiefly to parietals.............. UR x x xX 
Posterior to presphenoids and_ orbito- | 
SDHC OLS Maen see vies Seamer xX x 
Anterior to foramen proéticum (for V8) .. x x x xX 
External to Gasserian ganglia, or to sepa- 
rate trigeminal roots. . Mae | x x _ 2 
Chiefly posterior to 26 “es nerves, a 
1 Bi OE A [eG ae ea ly: x x x .4 
Postero-dorsal to pterygoids............. x x x xX 
Inferior wings laterally embracing basi- | 
sphenoid ::°.7 Capertee och 8 wee 2 x x x xe 
Inferior wings external to canals for ca- 
10) 3 0 Fe aE ROR oo). a ee x x x x 
—————— =- — — 
1X denotes definitely known agreement; x denotes probable agreement. 
— denotes disagreement. 
