1906.] IN MEXICAN LIZARDS. 305 



ISTew Mexico, and Arizona. " If we refer specimens with fewer 

 than 18 pores and no spots between the stripes or on the sides to 

 the C. sexUneatus, we find that in certain specimens from the 

 region in 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. gidaris, 



" In another series the post-antebrachial scales are equally inter- 

 mediate in size and there are no spots, but the femoral pores are 

 enlarged in numbers ; for instance, specimens from Santa Fe in 

 ISTew 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 intei'mediate links between 

 C. gularis and C. sexUneatus. 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. sexl'meatus, 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 with a more 

 polygonal forearm covering, and with a strong as well as a weak 

 collar. Better links are the 69 mm. specimen from Bloomington, 

 Illinois, and the 62 mm. specimen of 0. 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 mateiial 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, 

 moi'e granular forearm, and a weaker collar. Such small Ciiemi- 

 do2ihori are G. sexUneatus, common in the United States and 

 extending to the plains of ISTorthern Mexico, where they change, 

 or have changed, into C. gularis. 



Next comes the impoi'tant question lohether it is always 2Jossible 

 to distinguish C. sexlineatus yro?rt the less intensiHed specimens of 

 C. dep2)ei — 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 mm. 

 Forearm granular. 

 Supraoculars 4. 

 Femoral rows of scales not more than 6. 



