94. ORIGIN, ETC., OF THE FAUNA. 
Although South America must be regarded as the present headquarters of the 
Hystricomorphs, on account of the number and diversity of the genera that occur there, 
the group is not restricted to America. There are several African genera belonging 
to or closely allied to the Octodontide ; and Porcupines (Hystria, Atherura) are found 
in Tropical Asia as well as Africa. 
The paleontological history of the Hystricomorphs is very different from that of 
the other suborders of Rodentia. Genera regarded as ancestral members of the group, 
and constituting the family Theridomyide, were living in Europe from the Middle 
Eocene to the Upper Oligocene, and true Porcupines, related to the existing species of 
Hystrix, were in Europe in the Middle Miocene; but none of these extended into 
North America. On the other hand, genera assignable to the Octodontide and 
Erethizontine Porcupines suddenly appear in South America in Upper Miocene 
deposits—that is to say, considerably later than the date of the first known appearance 
of the group in Europe. The available evidence therefore points to the conclusion 
that this suborder made its way into South America from Africa, and subsequently 
spread northward into Central America and into North America, Erethizon dating 
from the Pleistocene in the latter country. 
Suborder LAGOMORPHA. 
The Ochotonide (Picas)—which occur in Central Asia and spread through Western 
North. America from Alaska to California, Utah, and Montana—do not enter Mexico. 
‘The Leporide have a much wider range. Three genera have been recorded from 
Central America, namely Lepus, Sylvilagus, and Romerolagus. ‘The last is mono- 
typical, and has been discovered at Puebla, Popocatepetl, etc., in Mexico at a height 
of 10,000 to 12,000 feet. Sylvilagus runs right through Central America from the 
Southern United States into South America. Jepus, in the modern sense, on the other 
hand, does not go south of Mexico (Durango, Tamaulipas, Potosi, etc.), whence it 
spreads northwards to Greenland and is also found in Asia, Europe, and Africa, 
The earliest paleontological records of Hares (Leporide) are from the Lower 
Oligocene of North America (Palwolagus). Lepus itself was in existence in the Upper 
Oligocene of that continent, and appeared in Europe in the Lower Pliocene. It seems 
therefore that this suborder of Rodents was evolved in North America, and thence 
made its way into the Old World and into Central and South America. 
Order CARNIVORA. 
_ The terrestrial or fissiped Carnivores of Central America belong to the five families 
Canide, Procyonide, Urside, Mustelide, and Felide. 
Canide:—The genus Canis is represented in North America by many species or 
local races belonging to groups typified by C. occidentalis and C. latrans, corresponding 
