A CUKIOUS 'TOAD. 91 



degree independent 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 glides 

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

 against the dry grass and brushwood, produces a rattling noise, 

 which can be distinctly heard at the distance of six feet. As often 

 as the animal was irritated or surprised, its tail was shaken ; and 

 the vibrations were extremely rapid. Even as long as the body 

 retained its irritability, a tendency to this habitual movement was 

 evident. This Trigonocephalus has, therefore, in some respects 

 the structure of a viper, with the habits of a rattlesnake: the 

 noise, however, being produced by a simpler device. The ex- 

 pression 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 anything more ugly, ex- 

 cepting, perhaps, some of the vampire bats. I imagine this repiil- 

 sive aspect originates from the features being placed in positions, 

 with respect to each other, somewhat proportional to those of the 

 human face ; and thus we obtain a scale of hideousness. 



Amongst the Eatrachian reptiles, I found only one little toad 

 (Phryniscus nigricans), which was most singular from its colour. 

 If we imagine, first, that it had been steeped in the blackest ink, 

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

 with the brightest vermilion, so as to colour the soles of its feet 

 and parts of its stomach, a good idea of its appearance will be 

 gained. If it had been an unnamed species, surely it ought to 

 have been called Diabolicus, for it is a fit toad to preach in the ear 

 of Eve. Instead of being nocturnal in its habits, as other toads 

 are, and living in damp obscure recesses, it crawls during the heat 

 of the day about the dry sand-hillocks and arid plains, where not 

 a single drop of water can be found. It must necessarily depend 

 on the dew for its moisture ; and this probably is absorbed by the 

 skin, for it is known, that these reptiles possess great powers of 

 cutaneous absorption. At Maldonado, I found one in a situation 

 nearly as dry as at Bahia Blanca, and thinking to give it a great 

 treat, carried it to a pool of water ; not only was the little animal 

 Tinable to swim, but, I think without help it would soon have 

 been drowned. 



Of lizards there were many kinds, but only one (Proctotretus 



