127 



most developed in the skull of the Myrmecobius fasaatus v^here the 

 orbit is large ; hut the bony boundary of the orbit is not complete 

 in any of the Marsupials. In the Myrmecobius there is a deep notch 

 at thl middle of the supra-orbital ridge. I have found the frontai 

 suture obliterated only in the Virginian Opossum and Petaunsts ; 

 but in the latter it is remarkable. that the other suturės of the head, 

 as the lambdoidal and sagittal, continue distmct. _ 



" The frontai bones are chiefly remarkable for their antenor expan- 

 sion, and the greatshare which they take in the fonnation of the na- 

 šai cavity. In the Thylacine the part of the cranium occupied by the 

 frontai sinuses exceeds in breadth the cerebral cavity. from whichit 



is divided by a constriction. . , . ■ • A-tv .„f i\fo^ 



" The lachiTmal bones vary in their relative size m different Mar- 

 supiata. lu the Koala they extend upon the face about a line be- 

 yond the anterior boundary of the orbit ; and at this part they pre- 

 sent a groove ^vūth one large. and two or three small perforat.ons ; 

 in the Wombat their extent upon the face is shghtly increased ; it 

 is proportionally greater in the Kangaroos, Potoroos, Phalangers, 

 and Dasyures, in which this part of the lachrj'mal bone presents two 

 perforations. but it is close to the orbit. The ^rhylacine. as compared 

 with the Wolf, presents a greater extent of the facial portion of the 

 lachrymal bone, and thus indicates its infenor tjTJe. ]n the Myr- 

 mecobius the lachrymal bone exhibits its greatest relative develop- 



""^'^ The malar bone is very strong and of great extent in all the 

 Marsupiata : least developed in the Perameles lagotis. it here presents 

 asingularform. being bifurcate at both extremities ; the procm«. 

 zygolaticus maxillce sup.erioris is ^vedged into the cleftof the ante- 

 rior fork ; the corresponding process of the temporal bone filis up 

 the posterior space ; the lower diA-ision of this bifurcation is the 

 lono-est and in all the Marsupiata enters mto the composition of the 

 articular surface for the lovver jaw, except in the Petaurists, Avhere 

 it iust falls short of this part. The anterior bifurcation of the malar 

 bone is not present in the Marsupiata generally : the external malo- 

 maxillary suture forms an oblique and almost straight line in the 

 Wombat, Phalanger, Opossum, Dasyurus, and Kangaroo. Owing 

 to the low development of the zygomatic process of the supenor 

 maxillary in the Wombat, the malar bone is not suspended in the 

 zveomatic arch in this Marsupial, as in the placentai Rodentia. lt 

 is of relatively much larger size, and of a prismatic form, ansmg 

 from the development of the obliąue extemalndge above descnbed. 

 In the Kangaroo. Potoroo. Great Petaurus, and Phalanger, it is tra- 

 versed externally by a ridge showing the extent of attachment of 

 the masseter ; in the Koala the ridge extends along the bone near 

 the upper margin, and the surface below presents a well-marked ex- 



""^TfThe'nasal bones vary in their form and relative size in the dif- 

 ferent eenera ; they are longest and narrowest in the Perameles. 

 shorTest and broadest in the Koala. Their most characteristic 

 smicture is the expansion of the upper and posterior extremity. 



