90 MR. E. R. AI.STON ON THE ORDER GLIRES. [Jail. 18, 



the tail flattened, lancet-shaped, covered with short hairs and not 

 tufted. No premolars. 



C. Pedetin.4;. One premolar above and below. Grinding-teeth 

 rootless. Cervical vertebrae free. Metatarsals separate. Hind feet 

 with four well-developed digits, with short broad hoof-like nails. 

 Tail bushy throughout, not tufted. Ethiopian. Recent genus : — 



5. Pedetes, Illiger, Prod. Syst. Mamm. p. 81 (1811). 



(Characters those of the subfamily.) 



Section III. Hystricomorpha. 

 One premolar above and below (except in Ctenodactylus). Grind- 

 ing-teeth rooted or rootless, not tuberculate. Frontals with no 

 distinct postorbital processes (except in Chcstomys). Infraorbital 

 opening large, subtriangular, or oval. Zygomatic arch propor- 

 tionally stout ; malar not advancing far forward (except in Cteno- 

 dactylina and Chinchillida), and not supported below by a continua- 

 tion of the maxillary zygomatic process. Incisive foramina small ; 

 foramina in base of skull proportionally large ; an interpterygoid 

 fissure. Mandible with its angular portion springing from the outer 

 side of the bony covering of the lower incisor, triangular, usually 

 pointed behind ; coronoid process small, and condyle low. Clavicles 

 perfect or imperfect. Fibula persistent as a distinct bone through- 

 out life. Upper hp rarely cleft. Muffle clad with fine hairs. Nostrils 

 pointed above, sigmoid or linear. Ears usually emarginate behind. 

 Tail hairy, subnaked, or scaly. 



Family I. Octodontid^. 

 Grinding-teeth with external and internal enamel-folds. Malar 

 with an inferior angle ; incisive foramina usually long, extending into 

 the maxillaries ; clavicles perfect. Both hind and fore feet usually 

 with five digits, rai'ely with four ; claws curved. Teats placed high 

 on the flanks. Tail clad with short hairs or with scales. Three 

 subfamilies : — 



A. Ctenodactylin^. Grinding-teeth semirooted. Malar ex- 

 tending to the lachrymal (as in the last family) in a flattened 

 perpendicular plate. Hind feet with the claws of the two inner 

 digits covered by comb-like series of bristles. Ethiopian. Recent 

 genera : — 



1. Ctenodactylus, Gray, Spicilegia Zoologica, p. 10 . . (1830). 

 Ears very small, with no antitragus. Tail rudimentary. Interparietal 



and auditory bullae large ; coronoid process reduced to a ridge. No 

 premolars. Molars with single external and internal enamel-folds. 



2. Pectinator, Blyth, J. A. S. B. xxiv. p. 294 (1855). 



Ears with a small antitragus. Tail half as long as the body, bushy. 



Interparietal smaller, auditory bullae larger, and palate more con- 

 tracted than in Ctenodactylus. Premolars present, but very small. 

 Third upper molar with two external folds. 



