REVIEW OF THE MODERN DOCTRINE OF EVOLUTION. 223 



foetal state all the Ruminantia (to wliich the camels belong) have 

 the cannon bones divided as in Poehrotheriiim ; they exhibit also 

 incisor teeth, as in that genus and Protolahis. Very young recent 



Fig. 13. — Protolahis transmontanus Cope, skull, a, in profile ; J, from below, one 

 third (linear) natural size. Original; from vol. iv, Report U. S. Geol. Surv., under 

 F. V. Hayden. Ticholeptus bed of Oregon. 



camels have the additional premolar of PUmicJienia. They shed 

 this tooth at an early period, but very rarely a camel is found 

 in which the tooth persists. The anterior premolar of the normal 



Fig. 14. — Procamelns occidentalis Leidy, profile of skull, about two sevenths natu- 

 ral size. Original ; from report of Capt. G. M. Wheeler, U. S. Geol. Geog. Surv. W. 

 of 100th Mer. Vol. iv, pt. ii. From Loup Fork bed of New Mexico. 



Camelus is in like manner found in the young lama (AucJienia), 

 but is shed long before the animal attains maturity. I may add 

 that in some species of Procamelus caducous scales of enamel 



