448 Zoological Society, 



its boundaries, as the corresponding superior vertebral lamina: com- 

 plete the medullary canal, in the region of the spine. I have found 

 the same structure and condition of the occipital bone of an adult 

 Dasyurus Ursinus, and it is exhibited in the plate of the cranium of 

 this species given by M. Temminck*. In the skull of a Perameles 

 nasuta the ex-occipitals were separated by an interspace, so that a 

 fissure was continued from the upper part of the foramen magnum to 

 the supra-occipital element. The same structure may be observed 

 in the Kangaroo, and is very remarkable in the young skulls of this 

 species ; I found this superior notch wide and well-marked in Ma- 

 cropus Bennettii. In the Wombat the corresponding fissure is very 

 wide, and the lower margin of the supra-occipital is notched, so 

 that the shape of thQ foramen magnum somewhat resembles that of 

 the trefoil leaf. In the Koala, the Phalanger, Petaurus, Hypsiprym- 

 nus, and Dasyurus Maugei, the elements of the occipital bone present 

 the usual state of bony confluence. 



" The temporal bone generally presents a permanent separation 

 of the squamous, petrous, and tympanic elements. I have observed 

 this reptile-like condition of the bone in the mature skulls of an 

 Ursine Dasyure, a Virginian Opossum, a Perameles, in different spe- 

 cies of Potoroo and Kangaroo, in the Wombat, and in the Koala. 

 So loose, indeed, is the connection of the tympanic bone, that, 

 without due care, it is very liable to be lost in preparing the skulls 

 of the Marsupiata. 



" In the Virginian Opossum the bony palate presents eight distinct 

 perforations besides the incisive foramina ; the palatal 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 dis- 

 tance (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 su- 

 ture ; lastly, there are two round perforations close to the posterior 

 margin of the bony palate. 



** Now there is no carnivorous quadruped in the placental 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 two small oblique canals, which open in 

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

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

 mammiferous remains hitherto discovered in the secondary formations, 

 * Monographic de Mammalogies pi. vIm. 



