ZOOLOGICAL POSITION. 15 
include the North American Cotton-Tail (Sylvilagus floridanus, 
Lepus sylvaticus), and the Prairie Hare or Jack-Rabbit (Lepus 
campestris) ; the European Common Rabbit (Oryctolagus cuni- 
culus), and Hare (Lepus europeus). The two European species 
differ in several well marked features, which form the basis of-the 
accepted distinctions between hares and rabbits. The rabbit is 
distinguished by its shorter ears and less elongated hind limbs; 
also by its burrowing habits, and by the circumstance that the 
young are born in a blind and naked condition. The hare is more 
nearly a running or cursorial type, and is distinguished by its longer 
ears—which, moreover, are tipped with black—longer hind limbs 
and prominent eyes. Unlike the rabbit it does not burrow, but 
inhabits only an open “‘form,’’ and the young when born are clothed 
with hair and able to see. 
The various species constituting this family are distinguished by 
several features, including the imperfect development of the 
clavicle, longer ears and limbs, and the presence of a distinct 
although greatly reduced tail, from the Picas or Tailless Hares 
(Ochodontide) of the mountainous districts of Central Asia and of 
North America (Rocky Mountains). The two families are allied, 
however, in the possession of a common feature, namely, the 
presence in the upper jaw of a second pair of incisor teeth. This 
feature distinguishes the sub-order Duplicidentata from that. of 
the Simplicidentata, the latter containing the majority of rodents 
and embracing all forms with a single pair of upper incisors. 
_ The mammalian order Rodentia, to which the family belongs, 
contains a very large assemblage of forms—the Squirrels, Marmots, 
Cavies, Beavers, Mice, and Porcupines being among the more 
familiar. This order is distinguished by the modification of the 
anterior incisors in both upper and lower jaws to form chisel-like 
cutting organs, the teeth having their enamel layer disposed 
chiefly if not wholly on their front surfaces, so that they remain ina 
permanently sharp condition. This modification is associated with 
an extensive obliteration of intermediate teeth, comprising posterior 
incisors, canines, and anterior premolars; also with elaboration 
and often great complexity of the remaining premolar and molar 
teeth, the lower jaw, and, indeed, the parts of the skull generally. 
Characteristic of these animals is the extension, both forward and 
