SINCLAIR : MARSUPIALIA OF THE SANTA CRUZ BEDS. 
337 
10. Optic foramen confluent with 
sphenoidal fissure. 
11. Basisphenoid and alisphenoid 
ridged as in existing marsupial 
carnivores and unlike the struc- 
ture of this region in the pla- 
centals. 
12. Posterior border of palate thick- 
ened. 
10. Not exclusively marsupial, al- 
though characteristic of that 
order. 
11. “In the marsupial Carnivora 
the basisphenoid is relatively 
longer than in the placental 
Carnivora , and, at its posterior 
part, it sends a ridge down- 
ward from that part of each 
lateral margin which is not 
overlapped or covered by the 
base of the alisphenoid, the 
suture of which long continues 
distinct. These ridges, with 
the alisphenoid, render the 
whole under surface of the 
basisphenoid canaliculate, or 
concave transversely ; the basi- 
sphenoid is flat beneath in the 
placental Carnivora , and that 
part of the base of the skull is 
made canaliculate by the de- 
velopment of the ectopterygoid 
plate from the alisphenoid ; 
these plates exist likewise in 
the marsupials, but, as they 
extend backwards to join the 
alisphenoid bullae, they diverge 
from the basisphenoid ridges 
and are external to them.” 
(Owen, Phil. Trans. Royal 
Soc. London, Vol. 149, p. 315, 
i860.) 
12. Characteristic of the majority of 
existing marsupials. Present 
also in some of the Creodonta 
(Mesonychidae). 
