892 DR. C. F. SONNTAG ON THE CLASSIFICATION 



shown on page 889, there are some resemblances between the teeth 

 of Phascolarctos and Phascolomys \A'hich have resulted from 

 convergence. These, however, must be excluded for purpose of 

 classification. 



Osteology : — The contrast in the skeletal characters are tabulated 

 as follows : — 



Phascolarctos and the Phalangeridae. 



1. Zygoma extended verticallj"^ and has 



no twist. 



2. Elements of occipital bone confluent. 



3. Characters of supra-occipital. 



4. Occipital processes arise from ex- 



occipital. 



5. Bulla from alisphenoid. 



6. Petrous has a large cerebellar pit. 



7. Six pieces in sternum. 



8. Characters of humerus. 



9. No third trochanter on femur. 



Phascolomys. 



1. Zygoma has a marked twist. 



2. Elements not all confluent in many 



skulls, but not in all. 



4. Processes from petro-mastoid. 



5. Bulla from temporal bone. 



6. Pit obsolete. 



7. Four pieces in sternum. 



9. Third trochanter present. . 



Myology : — Phascolomys differs from the Phalangeridee and 

 Phascolarctos in the absence of the quadratus femoris, obturator 

 internus and popliteus, and in having only one head to the rectus 

 femoris. 



Circulatory System : — Phascolomys has no trace of a vena 

 transversa (text-fig. 32). 



It is necessary to remark on the comparison between Phasco- 

 larctos and Pseudochirus, because these have been placed close 

 together in systems of classification. In a detailed examination 

 of their anatomy one finds they differ from other Phalangers and 

 Pliascolomys in the character of the teeth and straightening out 

 of the inflected angles of the mandible. As regards the visceral 

 anatomy and myology, there is no way in which they can be marked 

 out from other forms. I can see no reason other than the 

 condition of the teeth and mandible for separating Pseudochirus 

 from the other Phalangers, but I consider these alone as sufficiently 

 important to do so. 



When the characters mentioned in groups A and B are reduced 

 by the elimination of the unimportant ones the following lists are 

 obtained ; — 



A. Characters separating the Phascolarctidse from the Phalan- 

 geridae : — 



1. Supratragus, tarsal vibrissee, skin of pads and tail. 



2. Gastric gland patch and liver. 



3. Foetal membranes. 



4. Position of palatal foramina. 



5. Characters of symphysis menti. 



6. Characters of the mid-turbinal bone (Owen). 



7. Characters of the ear ossicles. 



