696 MR. R. I. POCOCK ON THE 



tolerably widely separable at this point. There is no median 

 excision in the interior edge of the rhinarinm above the teeth,, 

 and there is no median groove, but a groove runs on each side 

 from the nostril downwards and inwards to the gum, detining 

 the infranarial portion from the rest of the rhinarinm. 



Facial Vibrissoi. — The facial vibrissse are well and normally 

 developed in Trichosurus, Phalanger, Pseudochirus, and Fhasco- 

 lomys, being represented by numerous long mystacials, super- 

 ciliaries, gena.ls — one tuft, — submentals, and interraumls. In the 

 examples of Flialanger and Pseudochirus examined, however, the 

 interramals were few in number and slender. In Phascolarctos 

 the vibrissa} are comparatively poorly developed, the mystacials 

 especially being few and short and the interramal tuft wanting. 



Th6. Mouth. — There are only two points for me to notice in 

 connection with the mouth. The first is the presence, with which 

 everyone is familiar, of cheek-pouches in Phascolarctos. These lie 

 alongside the gum of the upper jaw in front, the orifice looking 

 downwards and the cavity extending upwards and backwards 

 towards the eye. No such pouches occur in Trichosurus, Pha- 

 langer, Pseicdochirtcs, or Phascolomys. The second is the presence 

 in Phascolomys of a flap of naked skin extending into the mouth 

 from the innei- surface of the lips laterall3^ This is analogous to- 

 the similar ingrowths well known in the Rodentia, where they 

 serve to close the throat during gnawing. Their function is no 

 doubt the same in Phascolomys. which has I'odent incisor teeth. 

 These oral flaps of skin are not developed in the other genera 

 here discussed, nor so far as I am aware in any other Marsupial. 



a. A flap of slcin jutting inwards from the lower lip and lying 



alongside the tongne on each side Fhascolomys. 



a'. No flap of skin jutting into mouth from the lips. 



6. A cheek-pouch on each side of tlie upper jaw JPhascolarctos. 



h'. No cheek-pouches Fseudochirus, 



PhalaHffer, Trichosuriis. 



The Ear. — In Trichosurus the ear is high, but tolerably narrow 

 and nearly naked internally. The supratragus (metatragus) is 

 a well-developed thick, semicircular, slightly upturned disk. 

 Above it there is a low curved ridge. In front of it the cavity 

 of the ear is defined by a strong oblique ridge passing upwards 

 slightly above the low ridge above described and inferiorly 

 curving backwards beneath the supratragus and passing thence 

 tlownwards on the inner side of the well-developed tragal 

 thickening forming the anterior rim of the inferior notch {aditus 

 inferior), the posterior border of which is defined by a strong 

 thick antitragal ridge, capable of being turned outwards and 

 backwards to a certain extent ; but it exhibits no pocket-like 

 depression. 



In Pseudochirus peregrinus the ear is nearly as naked intern- 

 ally, and relatively nearly as high as in Trichosurus but somewhat 

 broader. The supratragus is as well developed, but forms a more 

 distinct roof to the deep lower ^^ortion of the cavity. The low 



