676 



MB. F. G. PARSONS ON THE 



[Nov. 20, 



describes the teeth ; the latter figures the base of the skull in 

 A. africana and A. macrura, and mentions several points by which 

 they can be distinguished. The teeth of the animal I examined 

 agree with Gray's description, except that I was unable to make 

 out any folds on their hinder edge. The premolars were in the 

 process of being replaced by the permanent teeth, and this process 

 was much further advanced in the upper than in the lower jaw. 

 As I believe that the date of the shedding of the milk-premolars 

 is unknown, it may be worth recording that the following epiphysial 

 lines could be distinctly made out : — Upper end of humerus, lower 

 end of femur, tip of olecranon, lower end of radius, upper and 

 lower ends of tibia, lower end of fibula, hinder margin of ramus 

 of ischium. The epiphysis for the crest of the ilium had practically 

 disappeared. 



Eg. 1. 



Base of Skull, showing the temporary premolar tooth being replaced by the 



permanent one. 



a. Permanent premolar. 



b. Temporary premolar. 



In addition to the points noticed by Gray and Giinther, which it 

 is unnecessary to recapitulate here, there are one or two others 

 which seem of value in distinguishing the skull. In the first 

 place, in A. africana the frontal bone projects forward as a 

 triangular spine for some little distance between the nasal bones. 

 This characteristic was noticed in six out of seven skulls of 

 A. africana, while in only one out of four specimens of'^. macrura 

 was it present. All the other Porcupines which I have examined 

 have a straight suture between the nasals and the frontal. 



