622 The American Naturalist. [July, 
ON A SUPPOSED CASE OF PARALLELISM IN THE 
GENUS PALAEOSYOPS. 
By CHARLES EARLE! 
The object of the present paper is to attempt to show that 
in the extinct perissodactyle Palaeosyops, the species developed 
at least two parallel series, both of which may have lead to 
some permanent result. In other words, from a very thorough 
study of the known species of this genus, I am lead to the 
conclusion that the genus Titanotherium may have had a 
polyphyletic origin. This, will be impossible to prove until 
we know more of that intermediate form Diplacodon. 
Little has been attempted in the construction of the phylo- 
genies of species of fossil mammals, although a great deal has 
been done in this respect in regard to genera. I attempted it 
in my “ Memoir on Palaeosyops,” but the recent acquisition of 
new material proves that I made some mistakes in my phylo- 
genetie scheme. As our knowledge of Palaeosyops now stands, 
we know considerable about the structure of the skeleton in a 
number of well defined species, and in some cases the com- 
plete osteelogy is known. 
Professor Cope was one of the first to call attention to the 
phenomenon of the parallelism of genera. Professor Scott? in 
his series of valuable papers has placed before us a thorough 
exposition of what we have to attempt in paleontological 
investigation, and especially the relation of the latter to the 
facts of evolution. In the “ Deep River Mammals” he remarks? 
“only very rarely can we construct a phylogeny of species as 
distinguished from that of genera, and the latter are too vague 
for the purpose.” 
"American Museum of Natural History, New York. 
* Phylogeny of the Tylopoda. Journal of Morphology, Vol. ee 
Osteology of Mesohippus and Leptomeryx. Journal of Morphology. Vol. V, 
p. 301. 
The Mammalia of the Deep River Beds. Proc. Am. Phil. Soc., 1894. 
3 Page 119. 
