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 Pliilodendreae by Brandt, on account of the habit of living in trees 

 possessed by the species, may be characterized as follows : 



Cercoldbinae. 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 incisive 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. 



