RODENTIA—HYSTRICIDAE. 567 
provided with a distinct lachrymal bone which partly encloses the lachrymal foramen. The 
molars are semi-rooted, and arranged in parallel series; those of the upper jaw have one internal 
fold of enamel, and three or four folds entering from the opposite side of the tooth, but which 
soon assume the form of small isolated areas, disconnected with the margin of the tooth. The 
lower molars are like the upper, but with the enamel folds reversed. All the species are 
peculiar to the Old World. Genera Hystrix and Atherura. 
The next section, called Philodendreae by Brandt, on account of the habit of living in trees 
possessed by the species, may be characterized as follows : 
Cercolabinae.—Feet usually provided with but four toes, and these nearly equal in length, 
armed with long compressed curved claws; sometimes the hind foot has five toes. The soles 
of the feet are thickly studded with minute depressed warts. The upper lip not divided by a 
vertical groove. The skull is short and broad, provided with a minute lachrymal bone, which 
forms no part of the lachrymal canal; the portion of the palate which lies between the molars 
is distinctly on a lower level than the anterior portion, and the bony partition which separates 
the incisive openings, (being part of the intermaxillaries,) runs back above the palatal portion 
of the superior maxillary bones; whilst in the Old World porcupines the iucisive septum joins 
the superior maxillary by a serrated suture, and is continuous with the plane of the palate, 
which latter is throughout on the same level. (Distinct anterior and posterior clinoid processes 
bound the pituitary depression in the skulls of the Old World porcupines, but are wanting in 
the New World species.) The series of molar teeth of opposite sides of the jaw converge in 
front ; these teeth are distinctly rooted. Each molar has a distinct fold of enamel on either 
side, and the crown, when but little worn, presents a deep transverse cavity, surrounded by 
enamel on each of the two lobes, which are separated by the enamel folds. Incisor teeth small. 
To this division belong the genera Erethizon, Cercolabes, and Chaetomys, the latter differing 
considerably in the structure of its molars from the others, 
