498 



TREE PORCUPINES 



in both families we have long -tailed and short -tailed forms. 

 Cercolabes corresponds to Atherura or Trichys, and Erethizon 

 to Hystrix. 



The genus Erethizon, the " Urson " of Canada, has a short, 

 stumpy tail. Its spines are almost hidden by enveloping hair. 

 The fore-feet have four, the hind-feet five toes. The short tail of 

 this creature is remarkable when we reflect upon its climbing 

 habits. It appears, hpwever, to be a weapon with which it 

 strikes sideways at the enemy. 



Of the Neotropical genus Cercolabes (sometimes called Sphin- 

 gurus, Synetheres, or Coenclou) there are some eight or nine 

 species, all found in Central and South America. The animal is 



FIG. 244. Brazilian Tree Porcupine. Sphiiigurus prehensilis. xj. 



arboreal, and has in correspondence with that habit a prehensile 

 tail. The spines are not so stout as in the Ground Porcupines, 

 and are often coloured yellowish or reddish. In correlation with 

 its tree-frequenting habits the bones of Cercolabes show certain 

 differences from those of the Ground Porcupines. The scapula is 

 broader and rounder in front than is that of Hystrix; the 

 phalanges of the thumb (which is rudimentary) are fused 

 together as in the Canadian Erethizon ; but those of the very 

 small hallux are also fused, whereas in Erethizon, as in Hystrix, 

 they are separate. In one species, C. insidiosus, Sir W. Flower 

 states that there are as many as seventeen dorsal vertebrae 

 and thirty-six caudals. The tail is thus very long. In C. 

 villosus there are fifteen dorsals and twenty-seven caudals ; eight 

 ribs reach the sternum, which is composed of seven pieces, the 



