403 



Thomson and Mr. Krefft from the Breccia-cavern discovered by Sir Thomas L. 

 Mitchell, C.B. 



In a collection of marsupial fossils at Worcester I recognized a portion of the right 

 upper jaw, with the molar series, of a Macropus Titan exemplifying the stage of dentition 

 when the last molar as well as the premolar had come into place, but the former so 

 recently that the zygomatic pier had not much receded in position. The first and 

 second deciduous molars (d 2 and d 3) had been shed. The part of the series d 4 to m 2 

 inclusive occupied a space rather short of that containing the homologous teeth in the 

 younger specimen (fig. 10, ib.) ; but the structure of the last two teeth and the propor- 

 tions of the premolar were those of Macropus Titan. Unfortunately the crowns of the 

 first three teeth had suffered fracture. A portion of the hinder fold of enamel remained 

 on the broken base of the crown of the premolar, showing that the hind lobe of that 

 tooth, besides being thicker than the fore one, was divided into an outer and inner 

 lobule. Its longitudinal extent agreed with the crown of the germ of p 3 exposed in the 

 subject of fig. 6, Plate LXXXI. 



The same phase of dentition is exemplified in a similar portion of the right maxillary of 

 another and somewhat larger individual of Macropus Titan (ib. fig. 11), in which the 

 crown of the premolar is entire, and shows by its unworn condition that it had but 

 recently risen into place. This tooth instructively contrasts with the next grinder, 

 which is worn down so as to expose a continuous field of dentine, encroached upon by 

 two opposite folds of enamel from the inner and outer sides of the crown meeting at 

 the middle. In the next tooth the dentine is exposed upon each of the transverse 

 lobes and upon part of the anterior " link." In the penultimate molar a thin line of 

 dentine appears on the front lobe, but the enamel is not worn down so far in the hind 

 lobe. The enamel ridge of the front lobe of the last molar is touched by abrasion. The 

 crown of the premolar shows it to have been the last of the series of five teeth now come 

 into place. It is trilobed : externally it shows only the bilobed structure (as in fig. 6) ; 

 but there is a smaller third tubercle on the inner side of the hind lobe, increasing the 

 breadth of that part of the tooth, as was indicated by the last-described specimen 

 (Plate LXXXI. fig. 10,^3). The length of the entire series of five teeth is 2 inches 

 9 lines ; that of the premolar (fore-and-aft diameter of crown) is 5 lines, that of the 

 next tooth (d 4) being the same ; that of the penultimate molar is 8 lines. The whole 

 series is bounded on the inner side by an almost straight, very feebly concave, line ; the 

 outer contour is rather more convex. 



The two specimens above described are in the Museum of the Natural- History Society 

 of Worcester, to the Council of which I am indebted for the opportunity of describing 

 and figuring them. They were obtained by the donor, Henry Hughes, Esq., in the 

 freshwater deposits of Darling Downs. 



The subject of figs. 15, 16, & 17, Plate LXXXI., is also from the freshwater deposits of 

 Queensland. It includes a considerable proportion of the right maxillary, with the last 

 four grinders in situ, the dentine being exposed along a very narrow strip of the front 



