18 



TITANOTHEEES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



Species and subspecies of the genus Cervus 



[Table prepared by Qeirit S. Miller, 1918] 



COMPARISON BETWEEN ZOOLOGIC AND PALEONTOLOGIC 



SPECIES 



The difference between zoologic and paleontologic 

 species is represented in tlie accompanying diagram 

 (fig. 16), showing the descent and relationship of cer- 

 tain members of the dog family (Canidae). A theo- 

 retic stem or central form is shown from which geo- 

 graphic races have been given off horizontally, as it 

 were, and the ascending mutations and species of the 

 evolutionary line of development from the ancestral 

 form have arisen geologically. 



It follows that in making an anatomic comparison 

 between the existing geographic species and sub- 

 species of such genera as Peromyscus or Cervus and a 

 geologic phylum of species such as that of Menodus or 

 Brontotherium the same comparative anatomical 

 methods of measurement and observation should be 



employed. Direct measurements of the length and 

 breadth of the skull should be recorded, by which 

 indices (proportions of single structures like the skull) 

 and ratios (proportions between different parts like 

 the upper and lower segments of the limbs) should be 

 established. 



The proportional changes technically known as 

 dolichocephaly (elongation of the head), brachy- 

 cephaly (broadening of the head), dolichopy (elonga- 

 tion of the face), brachyopy (abbreviation of the 

 face), dolichopody (elongation of the feet), brachy- 

 pody (abbreviation of the feet), dolichomely (elonga- 

 tion of the limbs), brachymely (abbreviation of the 

 limbs) occur in geographic species and subspecies in 

 their corresponding stages exactly as they occur in 

 geologic phyletic time series. The chief difference is 

 that in the geologic time phyla these differences of 



