378 



preraaxillary suture the maxillary usually sends forward a sharp narrow process to be 

 wedged into the premaxillary, receiving into a notch below a similar process from that 

 bone. The suborbital canal divides into a dental and an antorbital canal. The anterior 

 outlet (ib. fig. 1, 21') of the antorbital canal, usually vertically oval in shape, varies in 

 its relative position to the orbit in different species of Kangaroo. A ridge near the 

 maxillo-malar suture leads to the zygomatic process, of which it forms the outer border. 

 This process (six) is the seat of variety, as to shape and size, in different species of 

 Macropodidse. 



The prcmaxillaries unite by a rhomboid facial plate (ib. fig. 1, 22) with, usually, the 

 terminal third of the nasals (15) and with the maxillarics (21). They develop sockets 

 for three pairs of incisors (i 1, 2, 3), and form the anterior end of the bony palate, which 

 is pierced by the " incisive foramina " (ib. fig. 3, 22-) in the form of oblong slits, closed 

 behind by the pointed ends of the palatal plates of the maxillaries. External to these 

 foramina the premaxillaries usually show a smaller foramen (ib. a'). 



The malar contributes the outer half of the floor of the orbit, articulating there with 

 the lacrymal and maxillary ; the zygomatic part of the malar (ib. fig. 1, 26) is deep or 

 vertically extended ; it articulates by an oblique suture with the maxillary pier of the 

 arch (21 x), and diverges to receive, by a large and deep notch, the pointed fore part of 

 the squamosal zygoma (27). The malar is excavated, as it were, below the orbital rim, 

 from which a ridge extends backward nearly parallel with the horizontal part of the 

 malo-squamosal suture ; the hind end of the malar expands horizontally or is produced 

 inward to form the fore part of the glenoid cavity (ib. fig. 3, 26x) or mandibular arti- 

 culation. The zygomatic part of the squamosal (27 ) rather exceeds in depth that of 

 the malar, rising abruptly behind from its attachment to the cranial part (27'). Close 

 to this attachment is the squamosal venous foramen (m) ; below this is a larger vacuity 

 (tympano-zygomatic cell, n) between the squamosal and tympanic ; and behind this is 

 the shallower " tympano-squamosal " cell. The cranial plate of the squamosal (27) 

 unites with the parietal and alisphenoid, with the superoccipital and mastoid, and with 

 the tympanic. 



The tympanic (PI. LXVI. fig. 1, 28) is a cylinder, expanding toward the brain-case into 

 an irregular triedral bone. The upper and fore side receives the postglenoid process ; 

 the under and outer part (ib. fig. 1, 28) articulates with the alisphenoid (e), the inner 

 part with the petrosal (ib. fig. 3, 16), the hinder part with the mastoid (8). The tym- 

 panic long retains its individuality. The auditory canal is directed outward and a 

 little upward and backward ; its outlet is circular ; but the canal loses vertical and 

 gains transverse extent as it passes inward. 



The pterygoid (ib. fig. 3, 24) has an antero-posteriorly extended base, which arti- 

 culates with the basi- and alisphenoids, completing the large concavity of the pterygoid 

 process of the alisphenoid and extending the hinder aperture of the nasal passage. The 

 lower end of the pterygoid articulates with the inner side of the pterygoid process of 



