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Show 1906.] IN MEXICAN LIZARDS. 305 New Mexico, and Arizona. " If we refer specimens with fewTer than 18 pores and no spots between the stripes or on the sides to the C. sexlineatus, we find that in certain specimens from the region h\ question [e. g. specimens from the Pecos River, from New Mexico, from Plateau Creek in Colorado, and from Fort Cobb in California] the post-antebrachial scales are larger than in the eastern specimens, though not so large as in the true C. gularis, " In another series the post-antebrachial scales are equally intermediate in size and there are no spots, but the femoral pores are enlarged in numbers ; for instance, specimens from Santa Fe in New Mexico, Camp Whipple in Arizona, and from Chihuahua. From these we pass easily to the true C. s. gularis, with large post-antebrachials and spotted spaces." This sounds rather conclusive, but when put to a more scrupulous test there appear difficulties. For instance, we should expect, from Cope's statement, that it should be the Chihuahua district which is inhabited by truly intermediate links between C. gularis and C. sexlineatus. But it so happens that the 4 Sauz specimens have in all only 129 pores, i.e. average 16*1 ; hereby, and by their spotless colour-pattern, they are well on the side of C. sexlineatus, while only one approaches C. gularis in the covering of the forearm ; and by their small number of femoral rows and in their small size these specimens stand quite alone. Moreover, the most enlarged polygones of the forearm are associated with only 15 pores. Specimens from Bloomington and San Diego show that a decidedly low number of pores can be associated wTith a more polygonal forearm covering, and with a strong as well as a weak collar. Better links are the 69 m m . specimen from Bloomington, Illinois, and the 62 m m . specimen of C. gularis from Duval County, Texas, and this specimen would be a perfect link if it had 18 instead of only 15 pores. If the enormous material in the Smithsonian Institute were examined properly, it would no doubt yield truly intermediate links. For the present, the best criterion is the absence or presence of pale field-spots. Absence of such spots is associated with a rather low number of femoral pores, more granular forearm, and a weaker collar. Such small Cnemidophori are C. sexlineatus, common in the United States and extending to the plains of Northern Mexico, where they change, or have changed, into C. gularis. Next comes the important question whether it is always jjossible to distinguish C. sexlineatus from the less intensified specimens of C. deppei-for instance, from such as have less than 8 stripes and have no black under parts. Such critical specimens must show the following characters:- Small size, below 70 m m. Forearm granular. Supraoculars 4. Femoral rows of scales not more than 6. |