SKELETON OF MAESUPIALIA. 343 



the Tliylacine, the Virginian Opossum, Cook's Phalanger, the 

 taguanoid, and yellow-bellied Petaurists ; but the frontal suture 

 exists in Petaurus sciureus, Acrohates, and other Marsupials. 

 The interorbital space is concave in the Phalangers and in the 

 Petaurus taguanoides, but is quite flat in the other Petaurists. 



The lacrymals vary in their relative size in different Marsupials. 

 In the Koala, fig. 221, 73, they extend uj^on the face about a line 

 beyond the anterior boundary of the orbit, and at this part they 

 present a groove mth one large and two or three small perfora- 

 tions. In the Wombat their extent upon the face is slightly 

 increased ; it is proportionally greater in the Kangaroos, Potoroos, 

 Phalangers, and Petaurists, in which this part of the lacrymal 

 bone presents two perforations close to the orbit. In the Thyla- 

 cine, besides the two external holes there is a large perforation 

 within the orbital margin. This carnivorous Marsupial, as com- 

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

 portion of the lacrymal bone, and thus indicates its inferior type. 

 In the Myrmecobius the lacrymal bone exhibits its greatest rela- 

 tive developement. The extraorbital lacrymal foramen is a good 

 marsupial character : it is present in the Thi/lacoleo, where it is 

 single, as in Dasyurus ursinus. 



The molars, figs. 220 and 221, 26, are very strong and of great 

 extent in almost all the Marsupialia. They are least developed 

 in Acrohates, fig. 219, Myrmecobius, and Perameles lagotis. In 

 the latter, fig. 222, the malar bone presents a singular form, being 

 bifurcate at both extremities : the processus zygomoticus maxillcB 

 superioris is wedged into the cleft of the anterior fork ; the cor- 

 responding process of the squamosal fills up the posterior notch. 

 The anterior bifurcation of the malar bone is not present in the 

 Marsupials generally : the external malo-maxillary suture forms 

 an oblique and almost straight line in the Wombat, Phalanr^er, 

 Opossum, Dasyures, and Kangaroo. Omng to the inferior deve- 

 lopement of the zygomatic process of the superior maxillary in 

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

 arch as in the Rodentia. It is also of relatively much larger size 

 and of a prismatic form, arising from the developement of the 

 oblique external ridge above described. In the Kano-aroos, 

 Potoroos, Great Petaurus, and Phalangers, it is traversed exter- 

 nally by a ridge showing the attachment of the masseter, of 

 which muscle the extent of origin is augmented by the descending 

 zygomatic process of the maxillary ; this is most developed in 

 the gigantic fossil Nototherc and Diprotodf^ii. 



The nasal bones vary in their form and relative size in the 



