352 PEOFESSOR OWEN ON THE SPECIES OF PHASCOLOMYS. 



that transverse parallel. Dr. Murie also notes the larger size of these foramina in 

 the skulls of Ph. latifrons which he compared with those of the platyrhine species '. 

 The intermolar part of the bony palate is more contracted anteriorly in the bare-nosed 

 (PI. LII. figs. 1, 4,21,21) than in the hairy-nosed Wombats (ib. fig. 5 21; PI. LII. 

 fig. 1, 21); the narrowest part is between the right and left second molars in Fh. 

 platyrhinus and Ph. vombatus; but in the Ph. latifrons there is little difference in 

 the interval between the second (di) and that between the fii'st (ds) molars. The 

 palate is slightly arched transversely, and is almost flat in some platyrhine Wombats. In 

 the latifront species it is always more vaulted, or deeper when viewed from below, at 

 the diastemal part (PI. LIU. fig. 1, 21), especially at the prepalatal openings (ib. a, a) than 

 in the bare-nosed species ; and the diastemal tract is more sharply defined, laterally, in 

 the hairy-nosed Wombat. The antorbital vacuity is wider, less slit-shaped, in Ph. lati- 

 frons than in Ph. platyrhinus (PI. L. fig. 1, 21) and Ph. vombatus. 



The cerebral cavity in Ph. latifrons (PI. LIU. fig. 5) is, in length, 3 inches 5 lines, and 

 equals one half the length of the cranium, which is 6 inches 9 lines in the specimen figured. 

 The cavity is divided by two vertical ridges into the epencephalic [e])), prosencephalic 

 (jyr), and rhinencephalic {rh) compartments. The petrosal (le) contributes a vertical sur- 

 face to the side of the epencephalic compartment, which is overarched by the superocci- 

 pital and parietal. The acoustic foramen or fossa is subcircular below the horizontal ridge 

 bisecting the cranial surface of the petrosal. The cerebellar pit above the ridge is 

 wider and more shallow than in Thylacinus and most other Marsupials ^. The ' vagal ' 

 foramen (ov) is between the petrosal and the exoccipital. Behind this, over the two or 

 three inner orifices of the precondyloid canals (^j), the foramen ovale (ot)), 8^ lines in 

 long diameter, perforates the alisphenoid below the tentorial ridge (5'), and opens out- 

 wardly anterior to the excavation forming the fore part of the tympanic cavity. A 

 groove runs forward from the foramen ovale to the foramen rotundum about 8 lines 

 in advance : at the inner side of this groove the basisphenoid is perforated by the ento- 

 carotid. From the inner orifice of this canal a gi-oove runs forward to the common 

 prelacerate and optic fissure {op). The rhinencephalic fossa (rh) is 7 lines in vertical 

 diameter, 5 lines in longitudinal extent. It has a large perforation at its lower and 

 back part leading to the common orbito-temporal fossa ; the floor and fore part of the 

 fossa are perforated by the smaller foramina transmitting the olfactory nerves to the 

 Eethmo-turbinals. The nasal cavity is di\'ided by a vertical septum extending from the 

 rhinencephalic cavities to 8 lines behind the tips of the nasals. The anterior border of 

 the septum is vertical, 1 inch in depth. In Ph. jjlatyrhinus the bony septum terminates 

 14 lines behind the tips of the nasals. The alisphenoid tentorial ridge is less developed 

 in that species. The sethmo-turbinals (e) form a mass about an inch in antero-posterior and 

 less in vertical diameter. The mid turbinal is elongate, developed from a ridge de- 

 scendiag from the roof of the nasal cavity, a short distance external to the septum, and 

 ' Proc. Zool. Soc. 1865, p. 848. ' ioc. cit. p. 390. 



