1857.] FALCONER — PLAGIAULAX. 2/3 



suppressed. It is now well known, that there is no certain distinctive 

 character, whether of placental or marsupial, that can be founded on 

 the number of their teeth. Among the marsupials, Myrmecobius 

 presents a case in which they are in excess ; while the Purl)eck 

 Plagiaulax would seem to present the opposite condition, where they 

 are below the normal number, from suppression. 



The same reasons are equally strong for referring Plagiaulax to 

 the neiohbourhood of the existing genus Hgjjsipri/tnnus. The affi- 

 nity indicated by the premolars and incisor is so manifest and direct, 

 that details upon the differences from other terms of comparison, 

 placental or marsupial, would be superfluous. The large grooved 

 premolar is confined among the Marsupialia to Hypsiprymnus ; 

 that genus, comprising three subgenera, includes about ten species, 

 in all of which the premolar is solitary, the true molars being con- 

 stantly four. In Plagiaulax there are either three or four grooved 

 .premolars, and only two true molars. In Acrobata and some of 

 the Phalangers, the inferior premolars are as many as four, the true 

 molars in these instances being reduced to three, a dentary formula 

 which closely approximates that of Plagiaulax ; while in other Pha- 

 langers the premolars are single, the true molars attaining the full 

 complement of four. 



In regard to the indications of the true molars, which might, a 

 priori, have been expected to be the most significant, the trituber- 

 cular antepenultimate, and the longitudinally two-edged last tooth 

 are without a known analogue among living forms. They certainly 

 bear no resemblance to any insectivorous species, placental or marsu- 

 pial. The general form of the tubercles of the antepenultimate sug- 

 gests some resemblance to the omnivorous pachyderms, but it is not 

 sufficiently pronounced to counterbalance the strong leaning of the 

 premolars to a herbivorous regimen. The wear of the two true 

 molars would seem to indicate a grinding, as contradistinguished 

 from a crushing or cutting action of the teeth ; and this is confirmed 

 by the form of the articulating surface of the condyle. 



The characters of the jaw are so peculiar, and in some respects 

 of so mixed and complex a nature, that they require to be weighed 

 wdth caution, in conjunction with teeth, in forming any opinion 

 regarding the affinities of Plagiaulax. The low position of the 

 condyle is so pronounced, and the elevation of the coronoid above 

 it so considerable, that regarded per se, supposing no teeth had been 

 discovered, they might have been considered to imply with some 

 degree of certainty, a predaceous animal. The condyle is even 

 relatively lower in Plag. Becklesii than in Thylacinus, Dasyurus, 

 and Didelphys, the most carnivorous among marsupial forms. A 

 condyle so placed was considered by Cuvier to be a positive indi- 

 cator of the ferine type. But in Plag. Becklesii, the force of the 

 indication is counterbalanced by another character, of which, so far 

 as I am aware, there is no example among any of the predaceous 

 genera, either placental or marsupial, recent or fossil, namely the 

 long neck and horizontal projection of the condyle behind the coro- 

 noid, the term "neck" being used for convenience to imply the con- 



