G. T. EETTANY OX THE GENES MERYCOCHCERES. 271 



especially of the inferior fork of the malar, it would appear that 

 they could not have extended outwards so far as in M, temporalis. 



5. The smaller size of the temporal fossae, and the more acute 

 angle (by about 10°) which its long axis makes with the middle 

 line of the skull. The cranium itself is considerably smaller in pro- 

 portion to the size of the skull than in M. temporalis. 



6. The postglenoid processes are much less broad and propor- 

 tionally deeper. 



The relative position of the auditory bullae, postglenoid processes, 

 and occipital condyles differs in the two species. A. line drawn 

 through the postglenoid and paroccipital processes to the middle 

 posterior point of the basioccipital in M. temporalis makes an angle 

 of about 60° with the median line ; the same angle is only about 

 45° in M. Leidyi. The absolute distance is greater in the latter; 

 and the postglenoid processes, instead of being opposite the middle 

 of the auditory bulla, are situated opposite its anterior extremity. 



The following are the dimensions of M. temporalis : — 



inches. 



Probable extreme length of skull 14 



Length of the larger portion in the "NYoodwardian 



Museum 9| 



Length of the small portion 7 J 



Half width across frontal surface 2| 



Distance from median line to external limit of zygo- 

 matic arch 5 



Greatest width of brain-case 3 J 



Width of palate within teeth 3 



Breadth between outer surfaces of postglenoid pro- 

 cesses o^ 



Depth of auditory bulla behind lg 



Depth of auditory bulla in front , 1 h 



Height of zygomatic crest 3^ 



Depth of skull in middle 4 



Probable depth at posterior extremity 5 



Longest diameter of orbit 2 



Depth of infraorbital arch \\ 



"Width of face just in front of orbit 2% 



Height of face in front 3| 



Length of last molar tooth If 



Dimensions of M. Leidyi : — 



Total length of skull (possibly the actual length was 



i inch greater when uninjured) 12k 



Half width across frontal surface 2 J 



Greatest width from middle line to exterior of zygoma, 



so far as existing 3 5 



Greatest width of brain-case 2£ 



"Width between external surfaces of postglenoid pro- 

 cesses 4g 



