74 ODONTOGRAPHY. 



size of The dimensions of the ultimate tooth in the great skeleton are : In the 



Sixth 



Tooth, lower jaw, seven inches antero-posteriorly ;* three inches and a half trans- 

 yersely ; seventeen inches around the neck. . In the upper jaw, seven inches 

 antero-posteriorly ; three inches and a half transversely ; sixteen inches and 

 three quarters around the neck. 



Besides these specimens, two of the upper, and two belonging to 

 the lower jaw, — making, in the whole, seven posterior molar teeth, — 

 give the same measurements. The casts of three ultimate molars afford 

 like results. Tavo others differed : one, having lost the anterior ridge by 

 use, was six inches long ; the second had the posterior ridge more developed 

 than in the other specimens, and measured eight inches. 

 Number Dr. Falconer says that the ultimate molar of the lower jaw is distin- 



of Ridges 



in sLxth guished from the corresponding one of the upper, by possessing five ridges, 

 instead of four. Not having noticed the existence of this distinction in so 

 decided a manner as expressed by this learned palaeontologist, we have 

 made a careful and repeated examination of many ultimate molars in our 

 possession, and find the following results : The ultimate lower molar, in 

 two entire full-grown heads, has four ridges and a talon ; in one, five ridges' 

 and a talon. In every case, the same is true of both sides. In four 

 portions of the lower jaw, it has four ridges and a talon. In the aged 

 Baltimore jaw, the tooth of the right side has four ridges without the talon. 

 In five casts of one ramus of the lower jaw, there are four ridges and a 

 talon to this tooth. In one cast, there are five ridges and a talon. In eight 

 ultimate molars not in place, there exist four ridges and a talon ; in two, 

 five ridges and a talon ; in one, five ridges without a talon. Thus Ave find, 

 that, in thirty-two ultimate teeth of the loAAer jaw, less than a quarter have 

 five distinct ridges. 



