246 



ELEMENTAR Y ANA TO MY. 



[LESS. 



these horny structures shed at intervals ; in the rest they 

 persist throughout life. Normally there is never more than 

 one pair amongst existing Ruminants, with the exception of 

 Antelope quadricornis, which has two pairs. Such horns 

 may be straight, or curved, or spirally twisted, but they are 

 never branched, with the single exception of the Prong- 

 horned Antelope. 



FIG 213. THE PANGOLIN (Manis). 



Less familiar, but not really more remarkable, is the struc- 

 ture developed in the scaly Manis or Pangolin. 



Here the entire body is covered and protected by strong, 

 sharp-edged, overlapping horny plates, each of which is 

 comparable with a nail. 



FIG. 214. TAIL OF RATTLESNAKE. 



The overlapping scales of Serpents are horny investments 

 of processes of the dermis, but the scales of Fishes are of 

 different nature, being formed in the dermis itself. 



