60 



ON THE EXTINCT MAMMALIA OF 



tunity of examining two additional skulls, together with the jaws of a third 

 individual of Ilycenodon crucians. All three specimens indicate larger animals than 

 any of those previously referred to this species. One of the skulls belonged to a very 

 aged individual, as exhibited in the extremely worn condition of the teeth, the 

 crowns of most of which have been obliterated. This sjoecimen is larger than any 

 others referred to H. crucians, and it presents a more marked development of all its 

 points of muscular attachment. The sagittal crest and anterior divergent temporal 

 ridges are relatively, as well as absolutely, very much stronger and more prominent 

 than in any of the other skulls. 



All the more complete specimens of Hyainodon crucians exhibit some variation in 

 the proportion of their parts. In the two first-described skulls the face differs in 

 being proportionately of greater length and depth, and less breadth than in the other, 

 and also in being less depressed or flattened above. In the two skulls last obtained 

 the face is more convex above than in either of the former; and it differs in them 

 in being proportionately longer and narrow-er in the smaller skull. 



Measurements derived from four skulls of Hycenodon crucians are as follows ; those 

 marked with an asterisk being estimated or approximative only : 



Length of temporal fossa along the middle. 



Breadth of cranium where narrowest. 



Breadth of forehead at post-orbital processes, 



Length of forehead from sagittal crest to nasals, 



Length of frontal in median line. 



Length of nasals. 



Breadth of nasals at frontal angular processes, 



" " at ends of premaxillaries. 



Height from palate to end of sagittal crest, 

 Distance from last molar to back end of nasals. 

 Distance from second premolar to internasal suture. 

 Breadth of face at ant-orbital margins, . 



" " at infra-orbital foramina, 



" " at canine alveoli, 



Height of orbit, 

 Height of end of nose. 

 Breadth of do., , 



Distance from ant-orbital margin to incisive alveoli. 

 Distance from post-glenoid tubercle to last molar. 

 Breadth at back extremity of alveolar borders. 







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crucians 







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