would point to a possible existence of two forms. 



This involves a question of the correct application of 



the fortunately few synonyms heretofore grouped 



under Testudo serpentina Linnaeus, which may 



be restricted to the northern or extremely keeled 



form. Clielydra lacertina Schweigger is virtually 



identical. The remaining Chelydra emarginata of 



Agassiz may then refer to the southern form, or at 



least to that common in the Delaware Valley 



and south. 



H. W. FOWLER, 



Philadelphia, Pa. 



COLOR CHANGES IN COLLARED 

 LIZARDS. 



Last summer it was my good fortune to be able 

 to study Bailey's Collared Lizard ( Crotapliijtes col- 

 laris) in the Painted Desert of northern Arizona. 

 Those which I observed were found only in locali- 

 ties where the volcanic or other rock occurred in 

 piles, or was scattered over the ground. The liz- 

 ards were generally seen perched upon one of these 

 rocks. During the cooler hours of the day they 

 were nearly always a dark, dirty gray, but when 

 the air was warm and the lizards became more ac- 

 tive, the color changed to a bright emerald green. 

 This was in the country of the sandstone rocks. 

 Where the black lava rock occurred the great 

 majority of the lizards were of the same dark color, 

 even when active and during the sunny part of the 

 day. In this latter country they were a perfect 

 example of protective coloration, but the green ones 

 seem quite conspicuous, unless one could imagine 

 a resemblance to the short grass, which occurred 

 irregularly. 



I have two specimens in captivity, and notice 

 this same color change during the day. In the 



