176 SNAKES. 



(which is a mere hardening and consohdatiori of the terminal 

 scales) and another feature, namely the ' pit ' in its cheeks, 

 described in chap, xxi., prove it to be allied to the rattle- 

 snake. It is therefore included among the Crotalidce, of 

 which more hereafter.^ 



A number of the ' Pit vipers ' and Trigonoccphall are 

 furnished with hard-pointed tails, and when they vibrate 

 them rapidly, as many snakes do under excitement, the 

 rustling against the dead leaves produces a sound very similar 

 to the sibilation of the true Crotaliis tail. 



TrigonoccpJialus contortrix, the ' Copper-head,' Is another 

 of these. Also the renowned ' Bushmaster ' of Guiana and 

 Brazil {LacJiesis inutus, or CrotaliLs mutus), of which latter 

 Darwin wrote, confirming Cuvier's reasons for making it a sub- 

 genus of the rattlesnake : — ' I observed a fact which appears 

 to me very curious, as showing how every character, even 

 though it may be independent of 

 structure, has a tendency to vary 

 by slow degrees. The extremity of 

 the tail of this snake is terminated 

 by a horny point, which is slightly 



Tail of Z.aMt'^/j ;«M2'7^s (exact size). 



enlarged, and as the anmial glides 



along, it constantly vibrates the last inch or so ; and this part, 



striking against the dry grass and brushwood, produces a 



^ The vipers in the London Gardens labelled Ctuchris piscivonis have not the 

 thorny tail, nor are they fish eaters. Nor can the spectator form any idea of 

 their swimming capacities, their dark, narrow tank barely enabling them to 

 extend themselves full length. Herpetologists differ in assigning the above name, 

 and in deciding which is really the ' Thoni-tail ' or ' Horn snake ' of Lawson and. 

 Catesby. Those at the Zoological Gardens, notwithstanding their specific name, 

 are never regaled on fish. 



