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BAHIA BLANCA. 



Aug. 1833. 



a pity to kill such nice little animals^ for as a Gaucho said, 

 while sharpening his knife on the back of one^, " Son tan 

 mansos'^ (they are so quiet). 



Of reptiles there are many kinds : one snake (a Trigono- ~ 

 cephalus^ or more properly a Cophias), from the size of the 

 poison channel in its fangs, must be very deadly. Cuvier, in 

 opposition to some other naturalists, makes this a sub-genus 

 of the rattlesnake, and intermediate between it and the viper. 

 In confirmation of this opinion, I observed a fact, which 

 appears to me very curious and instructive, as showing how 

 every character, even though it may be in some degree inde- 

 pendent of structure, has a tendency to vary by slow degrees. 

 The extremity of the tail of this snake is terminated by a 

 point, which is very slightly enlarged ; and as the animal 

 glided along, it constantly vibrated the last inch ; and this 

 part striking against the dry grass and brushwood, produced 

 a rattling noise, which could be distinctly heard at the dis- 

 tance of six feet. As often as the animal was irritated or 

 surprised, its tail was shaken ; and the vibrations were ex- 

 tremely rapid. Even as long as the body retained its irrita- 

 bility, a tendency to this habitual movement was evident. 

 This Trigonocephalus has, therefore, in some respects the 

 structure of Vipera, with the habits of a Crotalus ; the noise, 

 however, being produced by a simpler device. The expres- 

 sion of this snake^s face was hideous and fierce ; the pupil 

 consisted of a vertical slit in a mottled and coppery iris ; the 

 jaws were broad at the base, and the nose terminated in a 

 triangular projection. I do not think I ever saw any thing 

 more ugly, excepting, perhaps, in some of the vampire bats. 

 I imagine this repulsive aspect originates from the features 

 being placed in positions, with respect to each other, some- 

 what proportional to those of the human face ; and thus we 

 obtain a scale of beauty. 



Amongst the Batrachian reptiles, I found only one little 

 toad, which was most singular from its colour. If we ima- 

 gine, first, that it had been steeped in the blackest ink, and 

 then when dry, allowed to crawl over a board, freshly painted 



