86 FOSSIL MAMMALIA OF THE 



subjects of all the other illustrations of his ' Memoir,' marked as ' returned ' by the author. 

 The foregoing specimen (PI. IV, fig. 16), not described by Falconer, comes the nearest 

 to it, and at first I suspected that it might be such original from which the ascending 

 ramus and condyle had been accidentally broken away. But Falconer describes his 

 specimen as " Fig. 1, Plagicmlcuic Becklesii. The left ramus of the lower jaw, nearly 

 perfect, showing the outer surface, magnified 4 diameters," (loc. cit., p. 280^). But the 

 subject of my PI. IV, fig. IG, is clearly the fore part of the right ramus of the lower jaw ; 

 it differs also in the proportion of the premolars, in the relative depth of the ramus 

 supporting them, and more decidedly in the shape, size, and direction of the incisor. 



Dr. Falconer refers the specimen, fig. 14, p. 280, of his original Memoir, torn. cit. 

 and fig. 1, PI. XXXIV, of the undercited work, to his Plar/iaukuc Becklesii, and it will 

 be observed, in the copy of that figure, in Cut 12, p. 90, that the premolar {p 2) bears the 

 same proportion to 7; 3 as in the type of Plat/iaulax Becklesii, PI. IV, figs. 11, 11 a. 



The mandibular ramus with the incisor of Plagiaulax minor, restored according to 

 the analogy of Plagiaulax Becklesii, is, as we have seen, 1\ lines in length (fig. 6, p. 76). 

 The original of the fig. 14, p. 280, of Falconer's 'Memoir,' magn. 4 diam., must have 

 been 8 lines in length (fig. 7) ; it is nevertheless referred to Blagiaulax Becklesii 

 (PI. IV, figs. 10—14), which is 14 fines in length (fig. 8). 



Trusting, as we may confidently do, to the accuracy of Falconer's figure, it will be 

 seen that this differs not only, notably, in size from the type of the species to which that 

 minute and careful Observer refers it, but in the size of the premolar teeth. The series of 

 three in the type of Vlagiaidax Becklesii (fig. 8) has a longitudinal extent of 3 lines, 

 but in Plagiaulax medius (fig. 7) of 2^ lines. The shorter incisor (ib., i), tapering 

 from the exposed part of the base to the apex, might be interpreted as a stage in the 

 development and protrusion of the tooth ; and this probably led Dr. Falconer to suggest 

 that " the specimen would seem to have belonged to a young individual of PL Becklesii."' 



Fig. 7. Fig. 8. 



Plagiaulax medius. The subject of Falconer'a The type of Plagiaulax Becklesii, F. 



Plagiaulax Becklesii, fig. 14, loc. cit., Nat. size. 



reversed and reduced to the iiat. size. 



But the crowns of the premolars are fully formed and in place, that of the anterior one 

 ip 2) appearing to have been worn. Nothing that is known of the change of the den- 

 tition of the Marsupialia would support the inference that the premolars in fig. 7 were 

 of the deciduous series, destuied to be displaced by permanent ones of the size of those 



1 See also ' Paleeontological Memoirs and Notes of the late Hugh Falconer, .\.M., M.D., &c.,' 8vo., 

 1868, vol. ii, p. 41", pi. x.\xiv, fig. 1. 



- Loc. cit., p. 271, and ' Paloeontological Memoirs, &c.,' 1868, vol. ii, p. 421. 



