1857.] FALCONER — PLAGIAULAX. 269 



elevated strap-shaped coronoid of Hypsiprymnus and the other herbi- 

 vorous marsupials. It is to be remarked, however, that it is less 

 elevated, and that its surface is of less area, than in the predaceous 

 genera, whether marsupial or placental. 



Fortunately the condyle (^, fig. 4) is, in every respect, as perfect 

 as that of a recent bone. The matrix has been removed, so that 

 it stands out in bold relief, showing the convex articular surface 

 entire. In no part of the specimen are the peculiar characters of the 

 fossil more strongly marked than in this process, the remarkable 

 points being: 1st, its very depressed position, the upper edge being 

 below the line of the alveolar border, and the lower extending 

 nearly to the inferior margin of the jaw ; 2nd, its prominent 

 convex surface, great depth in proportion to the width, and vertical 

 direction ; 3rd, the breadth of the sigmoid notch (c?, e), involving 

 a long neck to the condyle, and its projection much behind the 

 coronoid process. The articular surface is convex and protuberant, 

 narrow in comparison to the height ; when viewed endwise, the out- 

 line is pyriform, the broad end being uppermost. The general 

 direction of the articular surface is vertical ; a chord through the 

 upper and lower edges of the curve would form a very acute angle 

 with a perpendicular immediately behind it. The neck-portion of 

 the sigmoid notch {d, e) is as long as the breadth of the coronoid, 

 so that the articular surface is not only depressed below the apex of 

 the coronoid, but projected a long way behind it. A line drawn 

 from the condyle to the gibbous prominence on the wall of the last 

 molar {i) considerably exceeds the length of the horizontal ramus 

 from the latter point on to the border of the incisive alveolus. The 

 inner surface of the ascending ramus behind the orifice of the dentary 

 canal {n) is smooth, and near its inferior border traversed by a longi- 

 tudinal channel which bends back to the under edge of the condyle. 

 The orifice of the canal {n) is low and directly in a vertical line with 

 the posterior wall of the last molar, being relatively situated exactly 

 as in Hypsiprymnus. The anterior margin of the canal forms a 

 raised step, the edge of which is continued upward in a low crescentic 

 ridge to join on with the base of the gibbous prominence of the last 

 alveolus. The mylo-hyoid groove traverses the ridge about the 

 middle, but the adhesion of the inner surface of the front piece («, b) 

 to the matrix does not at present admit of its being determined how 

 far the groove advances upon the horizontal ramus. The inner 

 surface of the coronoid is convex, which is partly obscured by the 

 plate of the process being traversed by numerous fissures, with 

 partial displacement of the pieces. 



The inferior margin of the hind part of the ramus is nearly hori- 

 zontal ; it terminates suddenly in the lower edge of the condyle. 

 A narrow fractured surface (fig. 4, o), the continuation of which was 

 evidently directed inwards {i. e. presented to the observer), is seen 

 on the side of the lower edge, stretching from the anterior boundary 

 of the dentary foramen {)i) on to the condyle. The rest of this in- 

 flected margin (what remains of it) is seen imbedded in the opposite 

 slab (fig, 1, h, o'). It forms a lamina of great tenuity. • The base 



