126 



cylindrical transverse canal characteristic of the ginglymoid joint of the lower jaw in 

 placental Carnivora. The surface, though of great transverse extent, was probably 

 carried out further in that direction by the malar bone (to judge by the analogy of 

 the Dasyurus (Plate XIV. fig. 2) ; but this part of the zygoma has been broken away. 

 There is a striking similarity, indeed, in the kind of mutilation which the fossil skull 

 from the freshwater deposits at Colungoolac (Plate XIV. fig. 1), and that from the 

 same formations channelled by the Condamine (Plate XVII.), has undergone. The 

 occipital condyles, zygomatic arches, and postorbital processes have suffered, differing 

 only in the degree in which these projecting parts have been broken away during the 

 apparently similar cosmical violence to which both fossils have been subject. Besides 

 the postglenoid ridge (Plate XVII. /) in Thylacoleo, there is a narrower boundary 

 wall descending in the inner or mesial end of the articular surface, nearly as low as the 

 posterior one ; it renders the surface concave in the transverse direction ; and against 

 this " entoglenoid process" (ib. e) abuts the apex of a thick obtuse triangular mass of 

 bone, with the base turned toward the descending basisphenoid ridge, but separated 

 from it and from the end of the pterygoid by a groove. This convex portion of bone 

 (Plate XVII. 6) appears to be developed from the base of the alisphenoid, and to have 

 contributed to the tympanic cavity, like the second "bulla ossea" in Per ame i 'es* ; it was 

 broken away on both sides in the first-described skull, but the pneumatic cavity by 

 which it was excavated is partly shown on the left side (Plate XIV. 6) ; its base is 

 perforated by the " foramen ovale." 



In the present skull the cranium has been broken across lengthwise, and almost 

 horizontally, exposing the extension of the air-sinuses (Plate XVIII. fig. 4) from the nose 

 to the occiput, raising the outer table of the cranium nearly 2 inches above the 

 inner one at the middle of the intertemporal ridge, and showing the small cerebral 

 cavity restricted to the lower and hinder half of the cranium. The length of this cavity 

 is 4 inches, its breadth 3 inches, its height 2 inches. Neither falx nor tentorium was 

 ossified. The anterior boundary of the " sella" is indicated by a transverse rising pro- 

 duced into a pair of small retroverted " clinoid" processes, but there is no depression 

 below the level of the cranial surface of the basisphenoid. The rhinencephalic com- 

 partment is relatively large. 



In all the characters of the cranium shown and described in the original specimen the 

 present fossil corresponds therewith. The posterior palatine vacuity, indicated by the 

 smoothly convex inner border of the roof of the mouth parallel with the hind half of 

 the sectorial tooth (in Plate XIV. fig. 1, d), is shown in the present skull (Plate XML d) 

 to be the fore part of the wide and advanced " palato-nares ; " they are divided, mesially, 

 by the presphenoid rostrum and vomer, and are bounded, laterally, by an extension 

 of the palatal process of the maxillary and of the palatine to the pterygoid. This 

 extension (ib. =o). flat below, convex above, contracts to a diameter of eight lines opposite 

 the middle of the posterior nostril, then increases in breadth, and loses in depth as it 

 * Cyclopaedia of Anatomy and Physiology, vol. iii. Art. Marsupialia, fig. 96. 



