it, and sucked with difficulty, and for some time, at them and the rump of the animal, until its jaws became so expanded, that, after this, it swallowed the whole remaining parts with apparent ease. Audubon then described the appearance that the snake presently assumed, which suggested "a rouleau of money, brought from both ends of a purse towards its centre," and its ineffectual attempts to move off; "when having cut a twig," he continued, "I went up to it, and tapped it on the head, which it raised, as well as its tail, and began for the first time to rattle." Now every careful reader of this remarkable story, provided he is at all conversant with the habits of snakes, will perceive that it could not possibly have been invented, for it is strictly and minutely in accord with facts, except in one important particular; the snake whose behavior Audubon watched and so accurately described was not the rattlesnake, but the blue racer or black snake (_Bascanion constrictor_); substitute "blue racer," for "rattlesnake," and this record is photographically correct.[61] The black snake does all the things which are here so minutely described—pursuing its prey with astounding agility, constricting about it as a prelude to swallowing it, ascending trees readily, coiling when brought to bay as if about to strike, and even vibrating the tip of its tail on the ground or leaves, as if in emulation of the genuine rattler, a kind of behavior which was looked upon by Darwin as a case of protective mimicry. No one could have known the rattlesnake better than Audubon from his constant encounters with it in the field; he made drawings of it, dissected its poison apparatus, and had kept it for months in confinement in order to study its habits; but by some curious twist of his notes or his memory, or led astray by the record made of the rattling habit, the species became confused in his published account. His error was gross and he paid dearly for it, but it certainly does not prove him to be the king of nature fakirs.