THE GENUS CNEMIDOPHORUS. 29 



/?/?. Femoral pores fewer than 15. 

 Femoral pores 12 ; 3 parietals ; B supraorbitals ; gray browa with 10 longitudinal stripes, 



G. multilineatus. 

 Femoral pores 9-11 ; 5 parietals; 4 supraoculars ; anals forming a triangle ; olive brown with 



6 stripes or some rows of spots C. ocellifer. 



aa. Anterior nasal plate reaching second labial. 

 Femoral pores 13 ; one marginal anal plate ; 6 white stripes ; small C. labialis. 



In this genus as in others, some characters which are constant in one species arc 

 inconstant in another. The presence or absence of the sixth infralabial, and of the 

 frenoorbital plates, are of this nature. The number of femoral pores varies within a 

 small range in all of the forms. Anomalies in the division of the head plates are 

 rare, but sometimes occur in this genus. Such are the fusion of the symphyseal 

 and f ostsymphyseal plates, the presence of an additional labial plate, etc. 



The discrimination of the IS'orth American species of this genus is the most 

 diflScult problem in our herpetology. l!^owhei-e are subspecies more clearly defined 

 than in Cnemidophorus, *'. e., definable geog?'aphical forms, which are not always true 

 to their characters. 



The color markings differ in the same individual at different ages, and the age at 

 which the adult coloration is assumed differs in different localities. Some of the 

 species, e. g., Cnemidopliorus sexUneatus, never abandon the coloration of the young of 

 other species and subspecies. The same condition is characteristic of the C. deppei of 

 Mexico, the C. lemniscatus of Brazil, and other species. The process of color modi- 

 fication is, as I have pointed out,* as follows : The young are longitudinally striped 

 with from two to four stripes on each side of the middle line. With increasing age, 

 light spots appear petween the stripes in the dark interspaces. In a later stage these 

 spots increase in transverse diameter, breaking up the dark bands into spots. In 

 some of the forms these dark spots extend themselves transversely and unite with 

 each other forming black cross-stripes of greater or less length. Thus we have be- 

 fore us the process by which a longitudinally striped coloration is transformed into a 

 transversely striped one. 



The large number of specimens of the C. tessellatus and C. gidaris in the 

 National Museum collection show that the breaking up of the striped coloration 

 appears first at the posterior part of the dorsal region {i. e., the sacral and lumbar). 

 The confluence of the spots appears there first; and finally (C. gularis semifasciatus), 

 where the color markings disappear, leaving a uniform hue, this also appears first at 

 the posterior part of the body. In the C. tessellatus rubidus the dark spots disappear 

 first on the anterior regions. 



* Proceeds. Araer. Philos. Soc, 1885, p. 283. 



