1906.] IN MEXICAN LIZARBS. 325 



Thirdly, the stripes have a tendency to break up first near 

 the root of the tail or rump, and this feature proceeds for- 

 wards. 



Fourth. The spots themselves can become effaced ; this likewise 

 proceeds from the rump forwards. In some very old specimens 

 the rump and lower back are uniform dull, and all that remains 

 of the 1st and 2nd pair of stripes are the pale greenish streaks 

 which border the dull-black field I. above and below. 



Fifth. These variations and changes are further complicated 

 by the gradual appearance of pale, never bright, small spots in 

 the dark fields, rarely in the black field I., often in fields II. and 

 III., especially on the lower back. These additional field-spots 

 give the lizards a much speckled and spotted appearance, if at 

 the same time some of the stripes are dissolved into spots. 



When I wrote the paper published in Proc. R. S. 1903, it was 

 easy to distinguish between a striped and a spotted race ; bvit 

 during my second collecting-tour in 1904, in the State of Guerrero, 

 I have brought together an ample number of specimens which 

 completely bridge the two extremes. The important facts are, 

 first, that the two varieties in their typical appearance are geo- 

 graphically distinct ; secondly, that the intermediate kinds occur 

 in those parts of Guerrero which geographically and physically 

 are also intermediate. 



The two extreme races are easily distinguished : — 



I. C gidtahis of Wiegmann * is the large spotted race, in which 

 the evanescence of stripes has reached its maximum. 



The important feature of this dull- coloured race are the complete 

 breaking up of the original 4th and 3rd pair of stripes into whitish- 

 yellow spots, the breaking up or fading of the 2nd and 1st pair, 

 and lastlj^ the disappearance of nearly all the spots from the root 

 of the tail forwards over the lower back. 



These changes are gradual and proceed regularly with age. Old 

 specimens show, moreover, partial confluence of neighbouring 

 spots of the 3rd and 4th rows ; a very interesting although 

 slight indication of a combination into a transverse or cross-bar 

 pattern. 



In very young specimens, about 40-50 mm. in length, from 

 Aguafria and San Juan Evangelista, all the under parts, including 

 the collar, are still uniformly white. Lines 1 and 2 are still 

 pronounced white stripes, although sometimes already broken into 

 short streaks and fading towards the arm. The original stripes 

 3 and 4 are already dissolved into rows of about 25 small, pale 

 dots, reaching from the neck to the tail. 



Such typical Cguttatus are known only from the open forests with 

 dense undergrowth, or similar patches of woodland, in the State of 

 Yera Cruz and its confines with those of Oaxaca. — It has the 



* Wiegmann's diagnosis, although not complete, is sufficient : " Cnemidophorus 

 cinevaceus guttis albidis in series 4 longitudinalibus dispositis, adspersus. Lateva 

 supenie vitta lata, stria pallide viridi supra infraque inclusa, intense nigrescenti ; 

 inferne maculis multis pallidis adspersa. ..." 



22* 



