P. BECKLESII AND P. MINOR. 421 



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 this 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 measure with that of the recent Hypsiprymnus. 



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

 specimen of Plagiaulax has been discovered by Mr. Beetles, 

 which supplies the desired information regarding the cha- 

 racters of the outer surface of the ascending ramus. See 

 fig. 1 of PI. XXXIV. 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 present, 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, 

 PL XXXIII. fig. 4 ; but a portion of the posterior margin is 

 probably wanting. The base of the coronoid is occupied by 

 a deep depression 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 terminates in 

 an excavation of the ramus common to it and the dentary 

 canal, as occurs in Hypsiprymnus. So far as can be seen, the 

 depression 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 speci- 

 men, magnified four times linear, is represented by fig. 1 of 

 PI. XXXIV. It bears out in every respect the marsupial 

 inferences deduced from the other specimens ; and indicates 

 for Plagiaulax a position between Hypsiprymnus and the 

 Phalangers.— June 20, 1857. H. F.] 



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

 represented by PI. XXXIV. fig. 2, a, b, magnified 4 diameters, 

 being double the scale of Plag. Becklesii, PL XXXIII. figs. 

 1 & 4. The outer side is exposed, the inner being adherent 

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

 horizontal ramus from the offset of the coronoid to the border 

 of the incisive alveolus, its great relative height on a line 

 with the premolars (p m), and the bold curve of the lower 



