1862.] FALCONER PLAGIATJLAX. 359 



with the jaw, appeared to me to counterbalance these indications : 

 namely, the moderate extent and low elevation of the coronoid above 

 the g-rin ding- plane of the teeth ; the long neck and horizontal pro- 

 jection of the condyle behind the coronoid ; the form of the condyle 

 itself; and the absence of a stout angular process behind it. With 

 one exception, I shall consider these mandibular characters briefly. 



And first, as regards the shortness of the horizontal ramus in pro- 

 portion to its depth. I refer my reader to fig. 20 of the accompany- 

 ing illustrations, representing the side view of the lower jaw of the 

 Aye-Aye. A glance will satisfy him that the horizontal ramus is 

 much deeper in proportion to the length in this form than it is in 

 P. BecHesii. The fact is so obvious that I do not think it necessary 

 to enter upon the metrical details. Commonly we connect the idea 

 of robustness in the lower jaw with the form and section of the 

 mandible presented by the Hyaena and Tiger. If the sections, 

 figs. 2 and 3, p. 278, of my original paper are referred to, it will be 

 seen that they are totally different. The jaw of Plagiaulaoo in this 

 respect also closely resembles that of the Aye- Aye *. 



The coronoid process comes next for consideration. For the de- 

 tails of my description of it, I refer my readers to p. 268 of my former 

 paper. It is there stated that " in general form the coronoid pro- 

 cess in Plagiaulaoc 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 

 coronoid of Hypsiprymnus and the other herbivorous marsupials. It 

 is to be remarked, however, that it is less elevated, and its surface of 

 less area, than in the predaceous genera, whether marsupial or pla- 

 cental." Here, it will be observed, the comparison was restricted to 

 marsupial forms, beyond which I did not then think it necessary to 

 carry it. If extended to the Aye-Aye (fig. 20), additional light is 

 thrown upon the character. In both, the anterior edge reclines at 

 an angle of about 45° ; in both, the summit is not much elevated 

 above the grinding-plane of the teeth. The appearance of elevation, 

 which is at first sight suggested by the coronoid of Plagiaulax, arises 

 from the great depth of the sigmoid notch and the low position of 

 the condyle. If fig. 1 of the illustrations of my former paper be re- 

 ferred to, it will be seen that the process itself is not raised much 

 above the summit of the premolars. There is a further agreement 

 between the Aye- Aye and Plagiaulaoc in the amount of area occupied 

 by the surface of the coronoid. This is partly disguised in the lower 

 jaw of the former, by the broad neck of the condyle, and the shallow- 

 ness of the lunate notch between it and the coronoid ; if the notch 

 were deepened, as indicated by the dotted line, the resemblance 

 would be complete. I do not, therefore, admit the force of Professor 

 Owen's remarks, as significant of carnivore affinities, that " the lower 



* In the Koala {Phascolarctus cinereus), in which the procumbent incisors, as 

 ah'cady observed (above, p. 353), are projected with an inclination resembHng 

 that of Plagiaulax minor, the horizontal rami of the lower jaw present great 

 deptli in proportion to tlie length, with a compressed section. (Waterhouse, 

 ' Mammalia,' vol. i. p. 264.) But the ascending ramus, in that genus, is on a 

 totally different plan of construction. 



