1857.] FALCONER — PLAGIAULAX. 2/1 



racters of the lower jaw of Flag. Becklesii. From the direction 

 which the fracture has invariably taken along the line of least re- 

 sistance, in two fragments on reversed slabs, whenever a complete 

 jaw has been discovered, and from the circumstance that the inner 

 surface has been always exposed, and the outer remained in adhesion 

 with the matrix, I am led to surmise that tliis has been caused by 

 the matrix forming a plug in the excavation here referred to, thus 

 causing it to adhere firmly ; and I am prepared to expect that the 

 outer surface of the ascending ramus will be found to agree in a great 

 mePvSure with that of the recent Hypsiprymnus. 



[P.S. Since the preceding remarks were written, a fifth specimen 

 of Plagiaulax has been discovered by Mr. Beckles, which supplies 

 the desired information regarding the characters of the outer surface 

 of the ascending ramus. See fig. 14, p. 280. It consists of the left 

 ramus, nearly entire from the incisor to the condyle, showing the 

 whole of the outer surface exposed. The specimen would seem to 

 have belonged to a young individual of PI. Becklesii. 



The incisor is vertically inserted, and projects above the level of 

 the premolars, of which there are three. The true molars, if pre- 

 sent, are concealed behind the flap formed by the anterior margin of 

 the coronoid process. This part of the jaw has been slightly crushed. 

 The coronoid process rises more vertically, and is narrower than in 

 the specimen, fig. 4 ; but a portion of the posterior margin is pro- 

 bably wanting. The base of the coronoid is occupied by a deep de- 

 pression bounded on the lower side by a raised ridge, which sweeps 

 round from the inferior part of the condyle, to be continued into the 

 anterior margin of the coronoid process. The characters are clearly 

 marsupial ; but it is not determinable whether the depression termi- 

 nates in an excavation of the ramus common to it and the dentary 

 canal, as occurs in Ilypsiprymnus. So far as can be seen, the de- 

 pression would seem to be more limited. The matrix has been 

 cleared away from the posterior inner margin, and a portion of the 

 inflected angle is distinctly visible. The specimen, magnified four 

 times linear, is represented by fig. 14. It bears out in every respect 

 the marsupial inferences deduced from the other specimens ; and in- 

 dicates for Plagiaulax a position between Hypsiprymnus and the 

 Pbalangers.— June 20, 1857. H. F.] 



The lower jaw of the other species, Plagiaulax minor, is represented 

 by fig. 15, a, b, magnified 4 diameters, being double the scale oi Plag. 

 Becklesii, figs. 1 & 4. The outer side is exposed, the inner being ad- 

 herent to the matrix. The notable points are — the shortness of the 

 horizontal ramus from the oifset of the coronoid to the border of the 

 incisive alveolus, its great relative height on a line with the premo- 

 lars {p m), and the bold curve of the lower margin. The incisor (a) 

 is projected with a less sudden curve upwards, and its sheath is longer 

 than in PI. Becklesii. The premolars are also larger in proportion to 

 the height of the jaw than in that species. Unluckily the whole of the 

 ascending ramus is wanting, and with it are lost the significant charac- 

 ters yielded by the form of the condyle, coronoid process, and poste- 

 rior angle. At the fractured posterior end (/;), a small portion remains 



