1896.] ANATOMY OF PETROGALE XANTHOPUS, 685 
molar is calcified and can be seen by cutting away the maxilla; it 
has not yet replaced the two premolars. The last (4th) molar is 
being cut. 
Fig. 1. 
Fag SUMP yA tha) AAR + ett Be Pe eee W mreea canta 
leak me) Spe OF T “a ps Py BA eek | 
Skull of Petrogale, showing os antiepilepticum. 
The Atlas agrees with that of most Kangaroos in wanting the 
foramen in the transverse process and in the incomplete ventral 
arch, which is ligamentous for about one-sixth of an inch. 
In an older specimen of the same animal I found this space 
reduced to a mere suture. The only Kangaroos in which I have 
found anything like a complete foramen in the transverse process 
are Hypsiprymnus and Bettongia. 
In the Awis the vertebrarterial foramen is incomplete, and I 
found a similar condition in an older animal. On looking at: the 
