418 



PLAGIAULAX. 



depressed disc of the outer surface of the ascending ramus, 

 although it may not have been continuous with it. 



The posterior fragment (b, d, fig. 4, PI. XXXIII.) shows 

 in very perfect preservation the whole of the inner surface 

 of the ascending ramus and condyle, with the exception of 

 the fragile edge of the inflected lower margin and angle, 

 which are broken off and left in part embedded in the matrix- 

 cast of the opposite slab containing the anterior fragment ; 

 it comprises also the posterior portion of the body, in which 

 the last molar is implanted. The coronoid process (e) is tri- 

 angular. Its anterior border slopes upwards and backwards 

 to the apex in a gentle curve, at an angle of about 45° with 

 the alveolar border. The posterior margin descends in a 

 curve with little deviation from the vertical into the broad 

 sigmoid notch (d, e), which is but slightly overarched by the 

 apex. 1 Its height and width at the base are nearly alike, 

 and about equal to the depth of the body of the jaw, in a 

 line with the last molar. The apex of the process is sharp. 

 In general form the coronoid process in Plagiaulax resembles 

 more that of the predaceous marsupials, and of the Ursine 

 Dasyurus especially, than that of the herbivorous families. 

 It differs very markedly from the elevated strap-shaped coro- 

 noid of Hypsiprymnus and the other herbivorous 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 (d, fig. 4, PI. XXXIII.) 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 

 (d, 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 outline 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 



1 The artist has represented the pos- 

 terior margin of the coronoid with too 

 crescentic a curve, and the point pro- 



jecting too much backward over the sig- 

 moid notch. 



