MR. U, LYDKKKKK ON LOWDK JAWS OF I»KOCOPTODON. 573 





Bingern sp. 



No. 40830. 



No. M. ."»()7C.. 





iuclies. 



iuclies. 



inches. 



Length of last 2 molars . . . 



1-83 



1-75 



1-5 



4 



315 



3-07 



2-80 



„ „ cheek-series . . . . 



3-7 



3-G 



3-4 



Greatest depth at symphysis 



. 2-(5 



2-4 



2-2 



„ width of jaw 



1-9 



1-8 



1-85 



These differences in size are obviously not such as can be considered 

 of specific importance. One of the distinctions between Procopto- 

 don and Macropus is the circumstance that the outer wall of the 

 masseteric fossa extends much higher up in the former than in the 

 latter, its summit reaching above the level of the molars, and thus 

 converting the fossa into a complete " pocket." The specimen ^N^o. 

 4G83G shows that the aperture of this ''pocket"' was comparatively 

 small. Both the latter specimen and No. M. 3676 (Phil. Trans, 

 for 1874, pi. Ixxvii.) also show that the small inflected " angle " of the 

 mandible was situated considerably below the level of the molar series, 

 and likewise that there is a marked ridge extending upwards and back- 

 wards from behind the last molar, so as to separate the channel lying 

 on the outer side of the molars from that part of the surface of the 

 jaw situated above the " angle." All the three specimens agree in 

 having the premolar of moderate length. 



A fragmentary left mandibular ramus, of which there is a cast in 

 the British Museum (No. M. 3674), containing the last two molars, 

 is described and figured by Owen in the Phil. Trans, for 1874, 

 pi. Ixxix. fig. 8, and pi. Ixxx. figs. 3-7, and referred to P. Goliah. 

 Although slightly larger than the Bingera specimen, this jaw agrees, 

 however, with the latter in the form of the extended molar channel ; 

 while its great thickness indicates that when entire it had the same 

 excessive relative depth. The length of the two molars of this 

 specimen is 1*95 inch, and its greatest breadth 2-1 inches. 



The resemblance to the Bingera specimen is, indeed, so close as to 

 forbid specific separation ; and we thus have a complete gradation 

 in point of size from this large jaw to the small No. M. 3676. We 

 may agree, therefore, to call all these four specimens provisionally 

 P. Baplia ; although as regards the size of the largest there is no 

 reason for separating them from P. Goliah. 



I now come to the second type of mandible from Bingera, which 

 is represented in PI. XXI. figs. 2 & 2a. The specimen is a right 

 ramus, which has lost the crowns of the first three cheek-teeth, but 

 in which the whole of the masseteric fossa is beautifully preserved. 

 A comparison of this specimen with the one represented in fig. 1 of 

 the plate will at once show that it is distinguished by the greater 

 relative length and much smaller depth of the horizontal ramus. A 

 comparison with the British Museum specimens Nos. 46836 and M. 

 3676 reveals further points of difference. Thus the aperture of the 

 masseteric "pocket "(fig. 2a) is very much larger in the present 

 specimen ; the*" angle '' (fig. 2, an.) is very .large, and situated in the 

 line of the molars ; while there is no well-marked channel between 



