174 



be admitted by candid readers of both my Papers on that genus that I have been reti- 

 cent of conjecture or assumption ; but I venture to say that when the limbs of Thyla- 

 coleo are restored they will not be " macropodal," not minimized at the fore part and 

 maximized at the hind part of the body, for bipedal saltatory actions to bear it swiftly 

 away from carnivorous pursuers, or to carry it far abroad from pasture to pasture and 

 from scrub to scrub in quest of vegetable food, but that they will agree in the main with 

 the limbs of Leo, Thylacmus, and Sarcophilus. 



Pursuing the comparison Thylacoleo with other Diprotodonts, we may at once dismiss 

 the arboreal Phascolarctidw, with a trenchant premolar (at least in the young Koalas), 

 on the same grounds as those on which the Pocphaga are rejected from the association. 

 The fallacious resemblance in the comparative views given in XII. pp. 312, 313, figs. 2 & 4, 

 of the skulls of the Koala and of the Thylacoleo (as restored by Professor Flower), 

 vanishes when they are turned from the front to the side view, as in figs. 6 & 8, p. 153. 



The sectorial of Phascolarctos forms one fifth of the molary series, and mainly through 

 •' the greater relative size than in other vegetable-feeding Diprotodonts of the four fol- 

 lowing molar teeth"*. The incisor formula differs by excess, as the premolar formula 

 does by defect, compared with the dentition of Thylacoleo, and this in the same way and 

 degree as in Kangaroos and Potoroos. 



We must pass to another family of Diprotodonts to find the two minute (I termed 

 them " functionless") premolarsf in advance of the last which retains its sectorial use 

 and equality of length with the succeeding molar. In Phalangista ursina, Ph. maculata, 

 and Ph. chrysorrhoa the functional premolar is preceded by two rudimental premolars. 

 In Phalangista Cookii (fig. 19) three minute teeth inter- 

 vene between^; \ and i, in the lower jaw, as in that of 

 Thylacoleo : in the upper jaw, where the canine is minute 

 and protrudes at the maxillo-premaxillary suture, two 

 small premolars intervene between it and the homologue 

 of the upper carnassial of Thylacoleo. The same degree 

 of correspondence in numerical formula is represented 

 by some Petaurists J ; but I have failed to find any spe- 

 cies of " Carpophaga " § in which three premolars appear Mandib ^jjjU ^gj 

 between the functional one and the canine, or any spe- 

 cies in which the upper incisors are reduced to two on each side. That a tendency 

 to deviate by such reduction was amongst the inconstant characters of organization of 

 diprotodont Marsupialia is exemplified by the Wombats, in which no incisors are 

 developed behind the large upper anterior pair. TJiylacoleo shows an interesting inter- 

 mediate stage of the incisive formula, viz. i. between the i.\E\ °f Phizophaga\\ and 

 the i. p5 of all other existing families of Diprotodonts. 



* Owen, " Classification of Marsupialia," Trans. Zool. Soc. (1839; p. 326. t Loc. cit. p. 323. 



i E. g. Petaurus (Belideus) fiaviventer, Cycl. of Anat. Art. Marsupialia, torn. cit. p. 264, f. 89. 



§ Owen, " Classification of Marsupialia, ," ut supra, p. 322. II Ibid. p. 329. 



