37G 



The base of the alisphenoid articulates with the side of the basisphenoid, leaving a 

 small hind part of that element clear for the entry of the entocarotid, and as small a 

 fore part for the exit of the optic nerve. From this attachment it extends backward 

 and forward, attaining an antero-posterior extent equalling that of the parietal. The 

 alisphenoid is pierced by the " foramen ovale " (tr) opposite the fore end of the petrosal, 

 and by the "foramen rotundum " near the fore part of its attachment to the 

 basisphenoid. The alisphenoid gains thickness and loses breadth as it extends back- 

 wards outside the cranial walls to articulate with the squamosal (27), tympanic (28), 

 mastoid ( 8 ), and paroccipitals ( 4 ), and contributes to form the tympanic cavity. The 

 thinner cranial plate ascends anterior to the squamosal to join the parietal, frontal, and 

 orbito-sphenoid. 



The sagittal suture (ib. fig. 2, 7') persists until maturity, its obliteration beginning 

 behind. Here the parietals (7) join the interparietal ( 3 x) and superoccipital (3'), 

 an intervening "fontanelle" long remaining, reduced to a fissure which is continued 

 between the mastoid and parietal ; it is usually obliterated in aged Kangaroos. 



The mastoid shows externally a narrow roughish vertical tract (PI. LXVI. fig. 1,8) 

 between the exoccipital ( 2 ) and post-tympanic base of the squamosal ( 27" ), which forms 

 the lateral border of the occipital plane (ib. fig. 4, 27), but not so broad a one as in Phas- 

 colomys (PL XLVI. figs. 2, 3, 4, 6, 7, 27). The upper end of the mastoid has a persistent 

 round venous aperture behind the masto-parietal fissure (PL LXVI. fig. 1, if). In front 

 of that fissure is the suprazygomatic venous foramen (ib. fig. 1, m). 



Each parietal (ib. fig. 2, 7) extends forward in a pointed form into a corresponding 

 notch of the frontal, the apex ending at the usual place of a postorbital process (ib. 

 fig. 2, 12), which is rarely developed in the Kangaroos, and is never large. The pre- 

 sphenoid (ib. fig. 3, 9) extends forward to coalesce with the "septum narium;" its hind 

 portion contributes to the optico-prelacerate foramen ; its fore part supports the small 

 orbito-sphenoid which completes that foramen, overarching it to join the alisphe- 

 noid, 6. 



The interfrontal suture (ib. fig. 2, 11) is persistent; even very old males of Macropus 

 major show a trace of it. Each frontal begins behind, narrow or pointed, expands as it 

 advances, and bends down more or less abruptly to form the inner wall of the orbit, 

 where it unites with the orbito-sphenoid (10), palatine (ib. fig. 1, 20x), maxillary (2i*x), 

 and lacrymal (73) ; anteriorly the broad end or base of the frontal joins that of the nasal 

 (15), and is wedged between the nasal (fig. 1, 15) and facial plate (21) of the maxillary. 

 The frontals contribute a small share to the anterior walls of the cranial cavity ; their 

 chief expansion is subservient to the development of the large and complex sinuses in 

 connexion with the olfactory cavity. This expansion is such in 21acropm antilopinus, 

 Gd., as to have suggested for it the subgeneric term Osphranter 1 ; it is somewhat less 

 developed in the present nearly allied species. 



1 Gr. ua<ppai rripms, sharp- smelling. 



