89 



premolar and the base of the jaw. Two small foramina are situated below 

 the position of the first premolar. 



In the American Journal of Science for 1871, 'Professor Marsh has 

 described the lower jaw, with teeth/ of a small pachyderm, under the name of 

 Lwmotherium lyrannus, which would appear at least to belong to the same 

 genus as' the former. The specimen was found near Dry Creek, Wyoming. 

 According to the description and measurements, the jaw nearly accords with 

 that of Notharctus tenebrosus. The teeth in an interrupted series consist of 

 two incisors, a canine, four premolars, and three molars. If we suppose 

 Notharctus to have two incisors, the number, character, and relative position 

 of the teeth agree in both. In Limnotherium the first and second premolars 

 are observed to have a single fang. This character alone would be insufficient 

 to distinguish a genus, and, perhaps, would hardly be regarded as a specific 

 character. The description of the molars of Limnotherium would apply to 

 those of Notharctus. 



The measurements of the lower-jaw specimen of Notharctus tenebrosus are 

 as follows : 



Liues. 



Length of jaw from condyle to incisive alveoli 30 



Depth of jaw below last molar 5f 



Depth of jaw below last premolar 6 



Length of symphysis 8 



Breadth of condyle • 3 



Anteroposterior diameter of condyle 2 



Length of dental series . 19£ 



Length of space occupied by the molar series 16 



Length of space occupied by the true molars 8f 



Diameter of canine at base of crown If 



Fore and aft diameter of second premolar li 



Transverse diameter of second premolar f 



Fore and aft diameter of third premolar ". If 



Transverse diameter of third premolar 1^ 



Fore and aft diameter of fourth premolar 2 



Transverse diameter of fourth premolar 1£ 



Fore and aft diameter of first molar ^ 2f 



Transverse diameter of first molar 2 



Fore and aft diameter of second molar 2f 



Transverse diameter of second molar 2 



Fore and aft diameter of third molar 3£ 



Transverse diameter of third molar 2 



In many respects the lower javv of Notharctus resembles that of some of* 

 the existing American monkeys quite as much as it does that of any of the 

 living pachyderms. Notharctus agrees with most of the American monkeys 

 12 G 



