511 



ramus in Dipr. Bennettii by reason of the minor height above the boss ; in this it is 

 2 inches, in Dipr. australis it is 2 inches 9 lines. 



In Dipr. Bennettii the ascending ramus begins gradually to rise from the antangular 

 inflection, and the lower border is continued by a regular and gentle convex curve to 

 the neck of the condyle, where it becomes gently concave. The sub- or post-crotaphyte 

 ridge gradually extends outward, but the thicker and most outstanding upper 3 inches 

 has suffered fracture. The coronoid process has been broken away. The thinnest part 

 of the lower border of the ramus is between the antangular inflection and the angular 

 one for an extent, viz., of 3 inches. The antangular inflection I reckon to be, in the 

 entire jaw, midway between the condyle and the outlet of the incisor socket. 



The neck of the condyle in the more slender jaw of Dipr. Bennettii is thicker than 

 that in Dipr. australis; the difference is as 1 inch 6 lines to 1 inch 1 line (measured 

 across the back part) ; it is also shorter in Dipr. Bennettii. The hinder third of the 

 base of the coronoid process is also thicker in Dipr. Bennettii than in Dipr. australis, 

 but the subcrotaphyte ridge is thicker in Dipr. australis. 



These latter differences incline me to the hypothesis that we have here an established 

 variety or species of Diprotodon; and it is the first evidence that has come under my 

 observation which seems to warrant such conclusion. 



The Diprotodon minor of Huxley* is founded on the teeth (ds, d 4) of species of 

 Nototherium (compare figs. 1-5, plate xxi. of the undercited Paper " On the Premolar 

 Teeth of Diprotodon, and on a new Species of that Genus " with Plate XLIII. figs. 3-5, 

 dz, di, and Plate LXXXVIII. figs. 11-16 of the present work). 



§ 5. Mandible and Teeth of a young animal. — In 1845 I described and figured a 

 series of teeth, discovered in sinking a well near Mount Macedon, Port Philipp, Pro- 

 vince of Victoria, referred them to a left ramus of the lower jaw of a young Diprotodon 

 australis, and described them as the four hinder molars (d i, m 1, m 2, m 3) of such jawf . 

 To the figures of this series was added (in Plate XXVI.) an anterior molar (d s), in 

 outline, to complete the view I then entertained of the entire molar series on one side 

 of both upper and lower jaws in that extinct species. I had no evidence in 1845 of 

 the molars then figured having belonged to one and the same individual, and their 

 determination was based on the nature of each individual tooth with consequent deduc- 

 tion as to the place it held in the molar series. 



I have lately received from my esteemed correspondent and indefatigable contributor 

 of materials for the present work, Dr. Bennett, F.L.S., an almost entire mandibular 

 ramus (Plate CXXIV.) of an immature Diprotodon australis, which exemplifies the 

 degree of abrasion of the molars answering to those above described, and fortunately 

 retains the small anterior molar (d 3) confirmatory of the restoration in Plate XXVI. 

 and of the sketch (ante, p. 204, fig. 2) transmitted to me by my friend Dr. Hobson. 



* Quarterly Journal of the Geological Society, vol. xviii. (1862) p. 422, pi. xxi. 



f Descriptive and illustrated Catalogue of the Fossil Mammals and Birds in the Museum of the Koyal 

 College of Surgeons of England, 4to, 1845, p. 309. nos. 1493-1496. 



