254? STUDY OF NATURAL HISTORY. 



modification of the same structure exemplified in 

 all the species of rhinoceros ; while the tusks of the 

 elephant are no more than teeth, performing the 

 same office, and applied to the same uses, as the 

 horns of the ox. Now it is very remarkable, that 

 naturalists agree in placing all these quadrupeds 

 close to each other ; or rather, in one of the primary 

 divisions of the class : so that, with the exception 

 of the morse and the monodon, or narwhal, the 

 whole of the horned quadrupeds are found belonging 

 to one natural order. This circumstance, of itself, 

 is a strong corroboration of the opinion here ex- 

 pressed, and should lead us to infer that horns and 

 such like appendages indicate one of the essential 

 characters of such groups or forms as possess them. 

 But where, the student may exclaim, are we to look 

 for horns among birds? for, if such appendages 

 really constitute essential characters, they must 

 either be found in other vertebrated animals, or a 

 structure, limited to one class, can never be ranked 

 as one of the primary types of nature. Now, the 

 only family of birds which may be said to possess 

 horns analogous to what we see among quadrupeds, 

 are the hornbills, JBuceridce, nearly all of which have 

 excrescences, as they appear, rising from the front 

 of the bill ; and one of the species is so remarkable 

 in this respect, that it is called the rhinoceros horn- 

 bill. - Other birds, — as the Tragopan pheasant of 

 India, the horned screamer of America, and the 

 unicorn chatterer of Brazil, — have hornlike pro- 

 tuberances, but they are soft and fleshy. The truth, 

 however, appears to be, that horns are represented 

 in the feathered tribes by crests, which are not 



