TYPES OF HORNS. 



3 



are consequently shed annually (or every few years) to be renewed 

 the following year, when, till the animal becomes past its prime, 

 they are larger than their predecessors. The periodical shedding 

 is also necessary in order to allow of this increase in size. With 

 the exception of the Reindeer, antlers are confined to the males. 



III. A third type of horn is presented by the American 

 Prongbuck, or Pronghorn, in which bony processes, or " cores," 

 corresponding to the horns of the Giraffe, have acquired a horny 

 sheath, in place of skin ; the sheath being in this instance forked, 

 and annually shed and renewed, although the core is simple. 

 The sheaths are akin to hair in structure, thus suggesting affinity 

 with the hairs surmounting the Giraffe's horns. Female Prong- 

 buck may or may not have horns. 



IV. In the great majority of " Hollow-horned Ruminants/' 

 such as Oxen, Sheep, Goats, and Antelopes, the horny sheath (or 

 true " horn ") forms a simple unbranched cone, which may be 

 compressed, spirally twisted, or curved in one or more directions, 

 but is permanently retained and continues to grow throughout life 

 from the base, while it becomes worn away at the tip. Some of 

 the leading modifications of this type of horn are shown in the 

 West Corridor and described in special labels. Rarely, as in 

 the Four-horned Antelope, there are two pairs of horns. In 

 many cases these horns are present in both sexes. 



V. The last type is that of the Rhinoceros, in which the one or 

 two unpaired horns consist throughout of "horny" matter (that 

 is to say, hair-like fibres closely welded together), with merely a 

 slight hollow at the base which fits upon a corresponding elevation 

 on the skull. Apparently this type of horn has had an entirely 

 independent origin, starting as a small horny nodule and gradually 

 increasing in size. The idea that it can have been derived from a 

 horn of the Ruminant type by the gradual dwindling of the core 

 and the solidification of the sheath seems to be negatived by the 

 fact that the early Rhinoceroses were hornless. These horns are 

 present in both sexes. 



b 2 



