206 The American Geologist. October, 1905 
dency of discovery will be to increase rather than to dimin- 
ish the number of contemporaneous independent phyla. 
Similarly the Eocene titanotheres instead of forming a suc- 
cessive monophyletic series, divide into four distinct phyla, 
to each of which a generic name must be given. Similarly 
again, the lower Oligocene titanotheres 4 , as shown in Fig. 
7, divide into four phyla, three of which have been traced in 
successive stages from the bottom to the summit of the 
Oligocene, each giving off several collaterals, all living in 
the same region and found in contiguous beds, but probably 
having a slightly different local habitat and habits. The 
law is illustrated again, as shown in Fig. 4, both in the Olig- 
ocene and Miocene horses ; in the Oligocene, for example, 
we have five contemporaneous lines of horses (Osborn ", 
Gidley), one of which includes the classic Ilesohippus 
hairdi of Leidy, which was long considered the single 
Oligocene horse, and figured as such in all phytogenies; in 
the Upper Miocene beside the Protohippus which still ap- 
parently is most nearly ancestral to Equus, we find as con- 
temporaries, the browsing, forest-living HypohippUs and 
the grazing and highly cursorial JVeohipparian, A compari- 
son of the phylogeny of the Camelidse (Fig. 5) published by 
Wortman 1 in 1898 on the monophyletic basis with that pub- 
lished by Matthew 2 in 1904 on the polyphyletic basis, shows 
the rapid progress which has been made in the demonstra- 
tion of the polyphyletic law. Similar results are apparent 
from our preliminary studies of the Proboscidiae in America. 
Many able contemporary workers, especially Schlosser and 
Deperet, are also bringing forth new illustrations of this law 
in Europe. 
3 New Miocene Rhinoceroses with Revision of Known Species. Bull. 
Amer. Mus. Nat. Hist:, vol. xx, 1904, pp. 307-326. 
4 The Four Phyla of Oligocene Titanotheres. Bull. Amer. Mus. Nat. 
Hist., vol. xvi, Feb. 1902, pp. 91-109. 
5 New O'igocene Horses. Bull. Amer. Mus. Nat. Hist., vol. xx, May, 
1901, un. 167-179. 
1 The Extinct Camellidae. Bull. Amer. Mus. Nat. Hist., vol. x. 1898, 
pp. 93-142. 
2 Xotice of two New Oligocene Camels. Bull. Amer. Mus. Nat. Hist., 
vol. xx, 1904, np. 211-215. 
