Wortman — Studies of .Eocene Mammalia. 399 



Art. XLI. — Studies of Eocene Mammalia in the Marsh 

 Collection, Peabody Museum • by J. L. Wortman. 



[Continued from p. 176.] 



Classification of the Primates. 



In dividing this order into it's primary branches, the first 

 and most necessary step is to obtain, if possible, a clear and 

 comprehensive understanding of the essential or fundamental 

 features which characterize the several lines upon the basis of 

 their evolution. It is naturally to be expected, that, as we 

 approach the point of common origin, these features will 

 become less and less accentuated, and those characters which 

 in the final development have become most pronounced, will 

 be found to be inconspicuous and apparently of little signifi- 

 cance in the beginning. 



It should be also remembered, that, while some of the phyla 

 have progressed along the lines of their final development 

 with comparative rapidity", and have modified many of the 

 characters which were more or less common to all Primates in 

 the earlier stages of their history, others have retained the 

 primitive features to a greater or less extent. Thus, the pres- 

 ence of such characters as an increased number of premolars, 

 the tritubercular condition of the molars, the small size of the 

 cerebral lobes, with the greater or less development of their 

 several parts, the presence of a floccular fossa of the skull, a 

 third trochanter of the femur, or an entepicondylar foramen 

 of the humerus, the possession of claws instead of nails on the 

 terminal phalanges, as well as many other similar characters, 

 are to be looked upon as common primitive features which 

 characterize all early Primates. Any one of the phyla may 

 have separately and independently modified these features 

 according to the requirements of a new environment. 



As an example in illustration of this statement, one might 

 meet with a Primate in which the premolars were much 

 reduced in number, in which the molars were fully quadri- 

 tubercular, the face much shortened, the brain highly devel- 

 oped, the temporal and orbital fossae separated by a bony 

 plate ; in short, in which might be found many of the charac- 

 ters of the most highly developed Primates ; but if, at the 

 same time, the specimen exhibited the peculiarities of the 

 incisors, canines, and the caniniform lower premolar, as well 

 as the cerebral circulation characteristic of the lemurs, one 

 could be perfectly certain that the species was genetically 

 related to and belonged in the Lemuroidea and was not a 



Am. Jour. Sci. — Fourth Series, Yol. XV, No. 89. — May, 1903. 

 27 



