PURBECK FORMATIONS. 97 



dental series, bespeak plainly the secondary or subsidiary function of the associated long 

 and large laniaries, as weapons, viz. of defence or of sexual combat. 



The true molars tell a similar story in every species of carpophagous and poephagous 

 Marsupial. Detached lower incisors of the Kangaroos are long, pointed, and shai-p-edged ; 

 in the Bettongs and Potoroos their tapering ends begin to manifest scalpriform 

 modifications. 



The procumbent, in many Kangaroos almost horizontal, position of these teeth warns 

 against the conclusion that they were made to pierce as weapons, offensive or defensive : 

 closely looked to and compared with true laniaries, such as those in Potamognle (figs. 16, 

 24) Thylacoleo (figs. 15, 18), and Plac/imdax (fig. 12), characters of shape and structure, 

 besides those of direction or position, are discerned in the incisors of Poephagans (figs. 10, 

 13,14) which relate to other ends than stabbing and tearing; to uses which require opposing 

 teeth of a different character and in greater number than in paucidentate Marsupials. 



The premolars of I*lagiaulax are plainly made to cut ; the strengthening of the 

 blade by enamel-ridges, and the serration of the cutting edge, due to their oblique 

 course, suggest an occasional application to tougher tissues than merely muscular. In 

 the trenchant and vertically grooved premolars of Potoroos and Bettongs the margin 

 is notched, but it has not the true serrate character which the oblique and unequally 

 bordered dentations give to the cutting edge of the carnassials of Plagiaidax. The three 

 or four such premolars in this genus combine their oblique serrate margins into a curved 

 line like that of part of a circular saw ; the notched edge of the single premolar in 

 Hypsiprymnus is straight. 



The many and large molar teeth and procumbent sub-scalpriform incisors associated 

 with the trenchant premolars of Potoroos and Bettongs, show the kind of substances these 

 were destined to cut. We know it to be tough, dry vegetable substances, such as the 

 coarse gi-asses of the XantJtorrhoea, the tegument of the Cycadeous Macrozamia, root- 

 fibres, &c. 



The few and small molar teeth and suberect laniariform incisors associated with the 

 serrate premolars of P/ffl^2«?//aa7 show that they operated upon animal tissues; the evidence 

 of the many and varied kinds of small Saurians coexisting with Playiaulax significantly 

 indicate the tough integument which such modified carnassials would be well fashioned 

 to divide. 



Trenchant premolars need not the ridged and serrate structure " for chopping up fruits 

 or succulent vegetables "^ the very perfection and strength given to the carnassials of the 

 little saurivore indicate the nature of the nutritive substances they operated on, and the 

 needlessness of supplemental pounding or masticating teeth in greater number or of greater 

 size than Plagiaulax possessed. Roots and grass " chopped up " by the premolars of 



' Flowek, Prof. Wm. Henry, F.R.S., " Ou the Affinities and probable Habits of the Extinct Australian 

 Marsupial, Thylacoleo carnifex, Owen," in ' Quarterly Journal of the Geological Society of London,' vol. xxiv 

 (18G8), p. 318. 



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