OMNIVORA. 347 



typical American Pig ; and in glancing at the forms that 

 preceded it in time, we cannot do better than quote the 

 remarks upon this subject made by Professor Marsh. After 

 stating that the oldest Artiodactyle Ungulate as yet known 

 in North America is the Lower Eocene Eoliyus, and that this 

 is an ancient representative of the Suida, this distinguished 

 palaeontologist proceeds as follows : ^ — 



" In the beds above, and possibly on the same horizon, 

 the genus Helohyus is not uncommon, and several species 

 are known. The molar teeth of this genus are very similar 

 to those of the Eocene HyracotJierium of Europe, which is 

 supposed to be a Perissodactyle, while Helohyus certainly is 

 not, but apparently a true lineal ancestor of the existing 

 Pigs. In every vigorous primitive type which was destined 

 to survive many geological changes, there seems to have 

 been a tendency to throw otf lateral branches, which became 

 highly specialised and soon died out, because they were un- 

 able to adapt themselves to new conditions. The narrow 

 path of tlie persistent Suilline type, throughout the whole 

 Tertiary, is strewn with the remains of sucli ambitious off- 

 shoots ; while the typical Pig, with an obstinacy never lost, 

 has held on in spite of catastrophes and evolution, and still 

 lives in America to-day. In the Lower Eocene we have 

 the genus Parahyus, apparently one of these short - lived 

 specialised branches. It attained a much greater size than 

 the true lineal forms, and the number of its teeth was much 

 reduced. In the Dinoceras beds, or Middle Eocene, we have 

 still, on or near the true line, Helohyus, which is the. last of 

 the series known from the American Eocene. All these 

 early Suillines, with the possible exception of Parahyus, ap- 

 pear to have had at least four toes, all of usable size. 



" In the Lower Miocene, we find the genus Perchoerus, 

 seemingly a true Suilline, and with it remains of a larger 

 form, Elothcrvmn, are abundant. The latter genus occurs in 

 Europe on nearly the same horizon, and the specimens known 

 from each continent agree closely in general characters. The 



^ Introduction and Succession of Vertebrate Life in America. An Address 

 delivered before the American Association for tlie Advancement of Science : 

 1877. 



