DUCKBILL. 



285 



is broad and somewhat flattened, with a coat of coarse hairs, which on the under 

 surface become more or less worn ofl' in old individuals. The short limbs have 

 their feet — more especially the front pair — expanded and webbed for the purpose 

 of swimming. Each foot has five complete toes furnished with strong nails ; but 

 while in the fore- feet the web extends considerably beyond the extremities of the 

 nails, in the hind-pair it reaches only to their bases. The extension of the web of 

 the fore-feet might appear to be a hindrance in burrowing ; but this difficulty is 

 avoided by the web being then folded back on the palm of the paw. The nails of 

 the fore-foot are somewhat flattened and expanded, while those of the hind-foot are 

 longer, narrower, and much curved. To the heel of the male is affixed a long, 



» 





THE DUCKBILL (} nat. size). 



horny spur, curving upwards and backwards, and nearly an inch in length. A 

 canal traversing this spur, and opening near its summit, is connected with a gland 

 on the leg, which appears to secrete a poisonous fluid. 



The tongue is small and non-extensile ; while the cheeks are provided with 

 pouches of considerable size, doubtless used for storing food. If it be a fully adult 

 specimen that we examine, it will be found that in lieu of teeth each jaw carries 

 two pairs of horny plates, of which the more anterior are sharp and narrow, while 

 those behind are broad and flattened. Between these plates the palate is thrown 

 into a number of transverse wrinkles, like those in a duck. In young specimens, 

 however, two or three pairs of cheek-teeth may be observed in the upper, and two 

 pairs in the lower jaw ; most of these teeth being broadly quadrangular in form, 

 with two cusps on one side, separated by a hollow from a longitudinal crenulated 

 ridge on the other. As these teeth are gradually worn away by the sand taken 

 into the mouth with the food, the horny plates grow up beneath and around them, 



