72 MEMOIBS OF THE QUEENSLAND MUSEUM. 



Xotothcrium. From the palation to the basion the distance is 220 mm. The 

 aperture of the posterior iiares at the palation is 53 mm. deep and about the 

 same in width. The posterior borders of the mesopterygoid fossa are incomplete, 

 but there was a depth of at least 65 mm. The walls of the fossa expand somewhat 

 in their course from the maxillary region. In section the fossa is U-shaped. 

 The external walls are marked with very prominent tubereules for muscle 

 attachments. On each side a large entocarotid foramen is to be seen, which 

 perforates the floor of the basisphenoid and enters the inner tables between 

 the Gasserian grooves, its course having been cleared on the left-hand side. 



The sutures between the basioceipital and basisphenoid on the inferior 

 surface can be traced at a distance of 83 mm. from the basion. The inferior 

 surface of the former bone is deeply concave, with a strong longitudinal ridge. 

 In its advance from the foramen magnum the bone somewhat narrows in breadth. 



The contours of the foramen magnum are not quite complete. The 

 transverse section is oval, with diameters (approximately) of 65 X 35. Botli 

 condyles are present, but only the right can be conjoined with its natural 

 surface. Its diameters are : jMaximum length 78 mm. ; extreme breadth -12 mm. 

 Unfortunately the lateral elements of the occiput are largely missing. 



The prominent condylar foramina are paired, being subequal, and 

 externally the openings are separated by a distance of 7 mm. It has been 

 suggested that the accessory foramen is homologous with those of the Creodonta. 



Interiorly the basioceipital and basisphenoid form a level platform about 

 65 mm. in width, but the supero-lateral elements are missing. On the external 

 border of the former may be seen, at the fractures, part of a large groove which 

 probably corresponds with the inner border of the jugular foramen. 



There are prominent grooves, slightly diverging anteriorly, for the 

 accommodation of the Gasserian ganglion; from the grooves posteriorly the 

 position of the foramen rotundum is barely indicated on each side. Anteriorly 

 the basal bones are incomplete, and the whole ethmoid region is missing. 



In the mature cranium of PhascoJomijs the cranial walls are greatly 

 thickened in the supra-occipital region, and large sinuses are present which are 

 not to be found or are but slightly developed in Macropns and Phascolarctns. 

 Our fossil resembles the wombats {Phascolomys) in this respect. The walls of 

 the cranium are surprisingly thick in this area and large sinuses are present. 



The internal tables of the cranium, in so far as they are available for 

 description, exhibit irregularities in the region of the sagittal suture. There 

 is an irregular median ridge, which is much distorted in the mid-parietal 

 region, probably associated with a sinus. The crania of many marsupials are 

 much thickened in the sagittal region. Anteriorly there is evidence of large 

 frontal sinuses. 



