512 ZOOLOGY BATRACHIANS AND KEI>TILES. 



"Blue Chaser" by the settlers, and greatly dreaded, for what reason we 

 were unable to ascertain, is quite common on marshy ground near the lake, 

 and Bascanhnn httcrnle is also of frequent occurrence, although not as nu- 

 merous as the preceding varieties. A singular fact was noticed in regard 

 to the serpents of this region, and the same observation will equally apply 

 to the lizards, viz : the extraordinary mimicry of color, depending in a great 

 measure upon the hue and tint of the surrounding objects; those specimens 

 seen upon the grassy meadows of the marshes being brilliant in color, assim- 

 ilating closely to the general tint of the herbage, while those found upon 

 alkaline plains were lighter, approaching the neutral tint of the ground and 

 sage brush. This fact was particularly noticeable in those serpents and 

 lizards found near red sandstone deposits, the normal colors being so much 

 altered and resembling the tint of the rock to such an extent as to lead to 

 grave doubts of the species under observation. In the course of a single 

 day's ride, we have noticed the little PJtrynosoma, or "Horned Toad", of the 

 same species, bearing three different solid body tints in as many different 

 localities : on the plain the prevailing color being greenish gray; on a stretch 

 of white alkaline flat nearly white ; and on red sandstone rocks so nearly 

 red as to almost escape notice. The most peculiar circumstance of this mim- 

 icry is, that after removal from the localities Avhere found, the normal colors 

 invariably return in twenty -four or forty-eight hours. This statement is 

 not merely conjecture, as the experiment was tried with a number of Phry- 

 nosoma of different tints, and found to be as represented. 



As already mentioned in the preliminary report, the rattle of the Crotalus 

 was frequently mistaken for the noise made by the Cicadas, although after 

 a short experience they were readily distinguishable by the difference of 

 rhythm ; that made by the Cicada being shorter and more uneven. The 

 rattling of this serpent was frequently heard without any apparent cause of 

 provocation, and may have been a sexual call for aught we know. In one 

 instance, a large rattlesnake was discovered beneath an "aparejo", or pack 

 saddle, coiled for a blow, but it had given not the slightest indication of its 

 presence by rattling. 



It is thought, with good reason, that the Crotalus is rapidly decreasing 

 in numbers on the western plains, or else that stories as to their former 



