204 MARSUTIALIA. 



Family MACROPODID^E. 



Dentition : I. ?, C. ( ~ } , Pm. f, H. J. The upper incisors are 

 secant, and arranged in a continuous arched series, distinctly sepa- 

 rated in the median line ; the first being often larger than either of 

 the others ; the lower incisor is secant and proclivous, and the 

 teeth of opposite sides frequently bite against one another. The 

 upper canine, when present, is often deciduous, and generally small. 

 The diastema is long. The premolars are either secant or triangular, 

 and in the former case are generally more or less distinctly marked 

 by nearly vertical grooves and ridges ; pm. 3 is always, and pm. 4 

 occasionally deciduous, the latter tooth being preceded by a milk- 

 molar. The true molars are either quadritubercular or transversely 

 ridged ; and m. 1 is occasionally deciduous. The mandible has a 

 deep pit and perforation in the masseteric fossa, and its condyle is 

 flat, transversely shortened, and not separated by a deep notch from 

 the coronoid process. The fore limbs are always shorter than the 

 hind ones, although their relative proportion varies much in the 

 different forms ; the scapula and humerus are frequently broad, and 



Fig. 35. 



Bettomgia grayi (Gould). Lateral view of skull ; from Australia. \. 

 (From the ' Quart. Journ. Geol. Soc.') 



the latter nearly always has an entepicondylar foramen. The olecra- 

 non is well developed ; the calcaneum and astragalus are of a peculiar 

 type, the former being characterized by the truncation of its distal 

 articular surface. The manus has five subequal digits ; but the 

 hind foot has the second and third digits much smaller than the 

 others, and enclosed in a common integument, the hallux being 

 absent in all recent forms except Hypsiprymnodon, and the fourth 

 digit always larger than either of the others. The femur is charac- 

 terized by a projection for muscular attachments at the outer side of 

 the external distal coudyle. 



