Section Iii.--Hystricomorpha, or Porcupine-Like Rodents.

With one exception (Ctenodactylus) have four molars in each upper and lower jaw; the tibia and fibula are distinct in young and old; the zygomatic arch is stout, and the malar does not advance far forward, nor is it supported by the maxillary zygomatic process; collar-bones perfect in some; the upper lip is rarely cleft; the muffle clad with fine hair; tail hairy, sub-naked or scaly.