MARSUPIALIA. 



273 



Skelete dcr Bculelth ie re; a small proportion of 

 their bony circumference is due to the anterior 

 extremity of the palatal process of the maxil- 

 lary : the same structure obtains in the Wom- 

 bat, Koala, and Opossums. In the Dasyures 

 and Phalangers a greater proportion of the 

 posterior boundary of the incisive or anterior 

 palatal foramina is formed by the maxillaries ; 

 in the Petaurists they are entirely surrounded 

 by the maxillary bones, while in the Perameles 

 they are, on the contrary, entirely included in 

 the intermaxillaries. They always present the 

 form of two longitudinal fissures : the Myrme- 

 cobius agrees with the other Marsupials in this 

 structure. 



The superior maxillary bone in the Wom- 

 bat sends upwards a long, narrow, irregular 

 nasal process, which joins the frontal and 

 nasal bones, separating them from the inter- 

 maxillaries; the part of the maxillary bone 

 which projects into the temporal fossa behind 

 the orbit presents two or three smooth tuberosi- 

 ties, formed by the thin plate of bone covering 

 the pulps of the large curved posterior grinders. 

 The corresponding part in the Peramtles Ingot is 

 is perforated by numerous minute apertures 

 like a cribriform plate, and this structure is 

 presented in a slighter degree in the Potoroos 

 and Ursine Dasyure. The antorbital foramen 

 does not present any marked variety of size, 

 which is generally moderate. It is much 

 closer to the orbit in the carnivorous Marsu- 

 pialia than in the corresponding placental 

 quadrupeds. It is relatively largest in the 

 Ursine Dasyure. It presents the form of a 

 vertical oblique fissure in the Wombat. I have 

 observed it double in the Kangaroo. The chief 

 differences in the maxillary bones, indepen- 

 dently of the teeth and their alveoli, are pre- 

 sented by the palatal processes, the modifica- 

 tions of which we shall consider in conjunction 

 with those presented by the palatal processes 

 of the palatal bones. The perforations and 

 vacuities of the bony palate deserve, indeed, 

 particular attention, as they are often specific 

 and of consequence in the determination both 

 of recent and fossil species. 



In Phalangista Cookii, in Petaurusjlavive.n- 

 ter, and Petuvrus sciureus, in Macropus major, 

 and some other great Kangaroos the bony 

 palate is of great extent and presents a smooth 

 surface, concave in every direction towards the 

 mouth ; it is pierced by the two posterior palatine 

 foramina at the anterior external angles of the 

 palatine bones, either within or close to the 

 transverse palato-maxillary sutures. Behind 

 these foramina, in the Kangaroo, there are a 

 few small irregular perforations. The bony 

 palate is similarly entire in the Hi/psipn/mnus 

 Ur sinus. In Macropus Henrietta there are four 

 orifices at the posterior part of the bony palate. 

 The two anterior ones are situated upon the 

 palato-maxillary suture, and are of an ovate 

 form with the small end forwards. The two 

 posterior foramina are of a less regular form 

 and smaller size. In the Brush Kangaroo 

 (Macropus Brunii, Cuv.) the posterior palatal 

 foramina present the form of two large fissures 

 placed obliquely and converging posteriorly. 



VOL. III. 



They encroach upon the posterior borders of 

 the maxillary plate. Anterior to these vacancies 

 there are two smaller foramina, and posterior 

 to them are one or two similar foramina. 



In the Australian Potoroos, Wombat, and 

 Koala, the posterior palatal openings are large 

 and oval, and situated entirely in the palatal 

 bones. In Hyps, setosus they extend as far for- 

 wards as the interspace between the first and 

 second true molars ; in Hyps, murinus they 

 reach to that between the second and third 

 true molars. Posterior and external to these 

 large vacuities there are two small perforations. 

 In the Phalangers, with the exception of Ph. 

 Cookii, the palatal openings are proportionally 

 larger; they extend into the palatal process of 

 the inaxillaries, and the thin bridge of bone 

 which divides the openings in the Potoroo, &c., 

 is wanting ; the two perforations at the pos- 

 terior external angles of the palatine bones are 

 also present. In the Virginian Opossum the 

 bony palate presents eight distinct perforations, 

 besides the incisive foramina ; the palatal pro- 

 cesses of the palatine bone extend as far for- 

 wards in the median line as the third molars : 

 a long and narrow fissure extends for an equal 

 distance (three lines) into the palatal processes 

 both of the palatines and maxillaries : behind 

 these fissures and nearer the median line are 

 two smaller oblong fissures ; external and a 

 little posterior to these are two similar fissures, 

 situated in the palato-maxillary suture ; lastly, 

 there are two round perforations close to the 

 posterior margin of the bony palate. 



In the Ursine Dasyure a large transversely 

 oblong aperture is situated at the posterior part 

 of the palatal processes of the maxillary bones, 

 and encroaches a little upon the palatines ; 

 this aperture is partly,* perhaps in young 

 skulls wholly, bisected by a narrow longitu- 

 dinal osseous bridge. In Mauge's Dasyure there 

 are two large ovate apertures crossing the palato- 

 maxillary sutures separated from each other 

 by a broad plate of bone ; posterior to these 

 are two apertures of similar size and form, 

 which, being situated nearer the mesial line, are 

 divided by a narrower osseous bridge ; each 

 posterior external angle of the bony palate is 

 also perforated by an oval aperture. In the 

 Viverrine Dasyure the two vacancies which 

 cross the palato-maxillary suture are in the 

 form of longitudinal fissures, corresponding to 

 the fourth and fifth grinders ; the posterior 

 margin of the bony palate has four small aper- 

 tures on the same transverse line. 



Now there is no carnivorous quadruped in the 

 placental series which has a bony palate cha- 

 racterized by perforations and vacuities of this 

 kind. In the Dog, the Cat, and the \Veasel-tribe 

 the bony palate is only perforated by two 

 small oblique canals which open in or near the 

 palato-maxillary suture. The very great in- 

 terest which is attached to the fossil remains of 

 the Stonesfield Marsupials, the only mammi- 



* The large aperture in the skull of the Da- 

 syurus iirsinus figured by Temminck is the result 

 of accidental injury to the bony palate. Mono- 

 graphics dc Mammalogie, pi. viii. 



T 



