272 



MARSUPIALIA. 



meles and Potoroos the sphenoid alze do not 

 reach the parietals. 



There is little to notice in the parietal bones 

 except the obliteration of the sagittal suture in 

 those species in which a bony crista is deve- 

 loped in the corresponding place. They pre- 

 sent a singularly flattened form in the Wombat, 

 in an aged skull of which, and in a similar one 

 in the Kangaroo, I observe a like obliteration 

 of the sagittal suture. In the Kangaroo, 

 Potoroo, Petaurus, Phalanger, and Myrme- 

 cobius there is a tiiangular inter-parietal bone. 

 The corresponding bone I find in three pieces 

 in the skull of a Wombat. 



the t frontal bones are chiefly remarkable for 

 their anterior expansion and the great share 

 which they take in the formation of the nasal 

 cavity. In the Thylacine the part of the cranium 

 occupied by the frontal sinuses exceeds in 

 breadth the cerebral cavity, from which it is 

 divided by a constriction. The coronal suture 

 presents in most of the Marsupials an irregular 

 angular course, forming a notch in the frontals 

 on each side which receives a corresponding 

 triangular process of each parietal bone : this 

 form of the suture is least pronounced in the 

 Acrobates and Myrmecobius. A process cor- 

 responding to the posterior frontal augments 

 the bony boundary of the orbit in the Thylacine, 

 tlie Ursine Dasyure, and in a slighter degree 

 in the Virginian Opossum ; it is relatively most 

 developed in the skull of the Myrmecobius 

 J'dsciutus, where the orbit is large; but the 

 bony boundary of the orbit is not complete in 

 any of the Marsupials. In the Myrmecobius 

 there is a deep notch at the middle of the 

 supra-orbital ridge. A corresponding but 

 shallower notch is present in the skull of 

 Petuurns sciureus. 1 have found the frontal 

 suture obliterated in old specimens of the 

 Thylacine, the Virginian Opossum, Cook's Pha- 

 langer, the taguanoid, and yellow-bellied Pe- 

 taurists; but the frontal suture exists in Petaurus 

 Sciureus, Acrobates, and other Marsupials. 

 The inter-orbital space is concave in the Pha- 

 langers and in the Petaurus Taguanoides, but 

 is quite flat in the other Petaurists. 



The lachrymal bones vary in their relative 

 size in different Marsupialia. In the Koala 

 they extend upon the face about a line beyond 

 the anterior boundary of the orbit, and at this 

 part they present a groove with one large and 

 two or three small perforations. In the Wom- 

 bat their extent upon the face is slightly in- 

 creased ; it is proportionally greater in the 

 Kangaroos, Potoroos, Phalangers, Petaurists, 

 and Dasyures, in which this part of the 

 lachrymal bone presents two perforations close 

 to the orbit. In the Thylacine, besides the 

 two external holes there is a large perforation 

 within the orbital margin. This carnivorous 

 Marsupial, as compared with the Wolf, pre- 

 sents a greater extent of the facial portion of 

 the lachrymal bone, and thus indicates its 

 inferior type. In the Myrmecobius the lachry- 

 mal bone exhibits its greatest relative develop- 

 ment. 



The malar b.;nes are very strong and of great 

 extent in almost all the Marsupialia. They 



are least developed in Acrobates, Myrme- 

 cobius, and Peramcles lagotis. In the latter 

 the malar bone presents a singular form, being 

 bifurcate at both extremities : the proccssus 

 zi/gomaticus maxilla superioris is wedged into 

 tiie cleft of the anterior fork ; the correspond- 

 ing process of the temporal bone lills up the 

 posterior notch ; the lower division of this 

 bifurcation is the longest, and in all the Mar- 

 supialia enters into the composition of the 

 articular surface for the lower jaw, except in 

 the Petaurists, where it just falls short of this 

 part. 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, 

 Phalanger, Opossum, Dasyures, and Kangaroo. 

 Owing to the inferior development of the zygo- 

 matic process of the superior maxillary in the 

 Wombat, the malar bone is not suspended in 

 the zygomatic arch in this Marsupial as in the 

 placental Rodentia. It is also of relatively 

 much larger size and of a prismatic form, 

 arising from the development of the oblique 

 external ridge above described. In the Kan- 

 garoos, Potoroos, Great Petanrus, and Pha- 

 langers it is traversed externally by a ridge 

 showing the extent of attachment of the 

 masseter ; in the Koala the ridge extends along 

 the malar bone near the upper margin, and the 

 surface below presents a well-marked excava- 

 tion. 



The nasal bones vary in their form and rela- 

 tive size in the different genera ; they are longest 

 and narrowest in the Perameles, shortest and 

 broadest in the Koala. Their most charac- 

 teristic structure is the expansion of their upper 

 and posterior extremity, which is well marked 

 in the Wombat, Myrmecobius, Petaurists, 

 Phalangers, Opossums and Dasyures. 



In the Potoroos the anterior extremities of 

 the nasal bones converge to a point which pro- 

 jects beyond the inter-maxillaries. In some 

 Petaurists and Perameles the corresponding 

 points reach as far as the inter-maxillaries, and 

 in a skull of the Perameles lagotis I have found 

 the bony case of the nasal passages to be further 

 increased by the presence of two small rostral 

 bones, resulting, as in the Hog, from ossification 

 of the nasal cartilage. 



The inter-maxillary bones always contain 

 teeth, and the ratio of the development of these 

 bones corresponds with the bulk of the dental 

 apparatus which they support. They are con- 

 sequently largest in the Wombat, where they 

 extend far upon the side of the face and are 

 articulated to a considerable proportion of the 

 nasal bones, but do not, as in the placental 

 Kodentia, reach the frontal or divide the 

 maxillary bone from the nasal. They pre- 

 sent a somewhat lower degree of development 

 in the Koala, but both in this species and 

 in the Wombat they bulge outwards and thus 

 remarkably increase the transverse diameter 

 of the osseous cavity of the nose. Neither 

 in Hi/psiprymnus nor Mucropus do I find 

 the incisive palatal foramina entirely in the 

 intermaxillary bones, as is described by the 

 author of the text in Pander and D'Alton's 



