129 



conseąuence in the detennination both of recent and fossil spe- 

 cies. 



" In Phalangista Cookii, some of the Petaurists, and the great 

 Kangaroo {Macropus Major), the bony palate is of great extent, and 

 presents a smooth surface, concave in every direction toward3 the 

 mouth ; this is pierced by two sraall posterior palatine foramina, 

 situated at the anterior extemal angles of the palatine bones, close 

 to the transverse palato-maxillary suturės ; behind the foramina in 

 the Kangaroo, and pierced in the suture itself in the Petaurists, are 

 a few small irregular perforations. The bony palate is also entire 

 in the Hypsiprymnus Ursinus, MviU. 



' ' In Macropus Bennettii there are four orifices at the posterior part of 

 the bony palate : the two anterior ones are situated upon the palato- 

 maxillary suture, of an ovateform, M'iththe 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 

 palatai foramina present the form of two large oval fissures placed 

 obliąuely, and converging posteriorly. They encroach upon the 

 posterior border of the maxillary plate. Anterior to these vacan- 

 cies there are two smaller foramina, and posterior to them are one 

 or two similar foramina. In the Australian Potoroos, Wombat, 

 and Koala, the posterior palatai openings are large and oval, and 

 situated entirely in the palatai bones ; posterior and external to 

 these there are two small perforations. In the Phalangers {Phal. 

 Cookii excepted) the palatai openings are proportionally larger ; they 

 extend into the palatai process of the maxillaries ; and the thin bridge 

 of bone •vvhich divides the openings in the Potoroo, &c. is wanting; 

 the two perforations at the posterior external angles of the palatine 

 bones are also present. In the Virginian Opossum the bony palate 

 presents eight distinet perforations besides the incisive foramina ; 

 the palatai processes of the palatine bone extend as far forwards 

 in the median line as the third molares ; a long and narrow fissure 

 extends for an equal distauce (three lines) into the palatai processes, 

 both of the palatines and maxillaries; behind these fissures, and 

 nearer the median line, are t\vo smaller oblong fissures ; extemal, 

 and a little posterior to these, are t\vo similar fissures, situated in 

 the palato-maxillary suture ; lastly, there are two round perforations 

 close to the posterior niargin of the bony palate. 



" Now there is no carnivorous quadruped in the placentai series 

 which has a bony palate characterized by perforations and vacuities 

 of this kind. In the dog, the cat, and the weasel tribe, the bony 

 palate is only perforated by t\vo small oblique canals, which open in 

 or near the palato-masillary suture. The very great interest which 

 is attached to the fossil jaws of the Stonesfield Marsupials, the only 

 mammiferousremains hitherto discovered in the secondaryformations, 

 •vvill justify the minuteness, perhaps tediousnesš, \vith which I have 

 dwelt on characters that, inclusive of the teeth, serve to distinguish 

 the craniiim of the iVIarsupial from that of any placentai quadruped. 

 The structure of the bony palate in the Marsupiata is interesting in 

 other respects. Sincc the defective condition of this part of the era- 



