Cope.] 332 fQ(,t -_ 



reach the complexity of those of the other line, of the Bovida^ or oxen, 

 nor do they become prismatic as iu that family, but retain the short crown 

 well distinguished from long roots, which belongs to all the earlier Mam 

 malia. 



The successional reduction in the numbers of premolar teeth in the 

 family of the Camelid* is shown in the following table.* There is seen 

 in the genera Protauchenia and Palauchenia a tendencj'' to an increase of 

 complication of the fourth inferior premolar : 



I. Premolar teeth |. 



Premolar i separated by diastema Procamelus Leidy. 



II. Premolar teeth |. 



Premolar ii below wanting PUauclienia Cope. 



III. Premolar teeth f. 



Fourth inferior premolar triangular Camelus Linn. 



Fourth inferior premolar composed of two crescents, which enclose a lake 



(an inferior premolar three ?) Palauclienia Owen. 



Fourth inferior premolar composed of two crescents, with two posterior 



tubercles behind them Protauchenia Branco. 



IV. Premolar teeth f . 



Fourth premolar below triangular Auchenia Illiger. 



V. Premolar teeth \. 



Fourth superior premolar composed of two crescents. . Holomeniscus Cope. 



The only genera which include existing species are Camelus and Au- 

 chenia, the camels and llamas respectively. It may be remarked that the 

 latter genus, which is confined to the new world, is more specialized than 

 Camelus, which is restricted to the old world. 



The succession of these genera in connection with the two preceding 

 families, may be presented as follows : 



No cannon bone. Cannon bone present. 



Incisor teeth present. Incisors one and two wanting. 



4 premolars. 3 prem's.f 2 prem's. 1 prem'r. 



Lower Miocene I Gornpliotherium 



fProtolabis 

 Pi'ocamelus 

 PUauchenia 



Camelus 

 Pliocene and recent 



Auchenia 

 This table shows that geological time has witnessed, in the history of 



*Froin Proceedings Amer. Philosoph. Soc, 1884, p. 16. 

 fin lower jaw. 



