400 Wortman — Studies of Eocene Mammalia in the 



member of the Anthropoidea.* We therefore finally come 

 to learn what the essential or fundamental characters really 

 are, and in proportion as our knowledge increases in this direc- 

 tion, in just that proportion shall we be able not only to 

 arrange the species, genera, families, etc., in their true and 

 proper relations to each other, but at the same time may 

 feel assured that such an arrangement represents something 

 more than a mere convenience. 



As long as we hold fast to the old horizontal system, our 

 classification will be artificial and unsatisfactory. This is 

 nevertheless ofttimes necessitated by our lack of knowledge, 

 but whenever evidence from the extinct forms is to be had, 

 sufficient to furnish even an incomplete glimpse at the phyletic 

 history, we shall always obtain much more satisfactory results 

 by arranging our classification accordingly. It is by reason of 

 this increase in our knowledge of extinct forms that frequent 

 innovations are necessary, in order to give some expression to 

 the general affiliations which the new discoveries reveal. Our 

 knowledge of the more exact relationships of the various rep- 

 resentatives of the Primates is still far from complete, yet I 

 am persuaded that a considerable advance over the older con- 

 ceptions is now not only possible but urgently demanded. 

 The classification herein proposed introduces some novel fea- 

 tures, which may or may not stand the test and be justified 

 by future discovery, but it none the less denotes an effort to 

 give expression to some of the genetic affinities of the several 

 known types of the order, which a study of the extinct forms 

 reveals. 



It has been customary to include among the Primates the 

 North American Hyopsodidse, a small family containing two 

 genera and some four or five species, which are limited in 

 their vertical distribution to the Middle and Upper Eocene 

 strata. Hitherto, nothing has been known of the skeleton, and 

 consequently they have been placed in various positions within 

 the order. In the skull, of which a fairly complete specimen 

 was found by me in the Washakie Basin, Wyoming, in 1895, 

 and is now preserved in the collections of the American 

 Museum, there is no ossified tympanic bulla, and the carotid 

 canal enters the cranium as in the Insectivora. The forame?i 

 ovale is placed well within the alisphenoid, and is not a notch 



* Such an example was, in fact, an actual occurrence. Dr. Forsyth Major 

 discovered an extinct Primate in Madagascar, which he named Nesopithecus. 

 From the unusually high development of the skull, and its many resem- 

 blances to the higher apes, he concluded that it was an Anthropoid. 

 Lydekker, however, justly criticised this view, and pointed out that, owing 

 to the distinctly lemurine character of the incisors and the caniniform 

 enlargement of the first lower premolar, it should be classed as a highly 

 developed Lemuroid. 



