1906.] IN MEXrCAN LIZARDS. 341 



of granules at the hinder edge. Posterior side of foreamn with 

 large scvites in at least one row. — Consequently these specimens 

 combine the intensified features of the C gidaris group. 



The immature have 6 clear whitish stripes, and faint brownish 

 spots in the very dai-k, almost black first and second fields. The 

 centre-field 3-3 is also black, with a short white centi-e streak on the 

 nape and neck, and this streak is in one specimen continued upon 

 the back by a double row of pale spots ; in another it is continued 

 as a dull unpaired stripe. These variations demonstrate the 

 possibility of 7 to 8 stripes in all. — In the 88 mm. specimen 

 all the stripes are redviced to faint lines on the neck. The rest 

 of the back shows a uniformly black ground with numerous 

 whitish spots in about 10 rows ; the thighs are similarly spotted. 



In the oldest specimen (97 mm.) the ground-colour is very dark, 

 blackish, with numerous, very conspicuous white and bluish round 

 spots in 10 or 11 rows. The three pairs of stripes are faintly 

 visible on the neck, where the spots are far less pronounced. 

 Throat and collar are pink. Rest of under parts, including the 

 arms, blue-black, mottled with particoloured scales. Tail bluish 

 beneath. 



This 97 mm. specimen much resembles a 90 mm. specimen from 

 Lerdo, near Torreon ; this town would, with our present state 

 of knowledge, represent the North-eastern limit of the typical 

 C. communis. 



The collar of the Lerdo specimens is composed of large scales, 

 without granules. Throat of the adidt red-pink ; sides of collar 

 grey. Rest of under parts, including thighs, blue-black with 

 whitish scale-edges. Tail bluish. — Above : the smaller specimen 

 with 6 complete stripes and a pale centre-line. Double rows of 

 grey-brownish spots in the dark fields. In the larger specimen 

 the stripes have disappeared completely ; ground-colour black, 

 with numerous bluish-white spots, arranged in rows, from neck 

 to tail. Sides of trunk with black and light bars, some of which 

 reach far upon the back. 



Ixtlan. — The specimens were collected by Dr. Buller near the 

 River Santiago, near the confines of the State of Jalisco and the 

 Territory of^Tepic, at altitudes from 1500 to 3500 feet. This 

 district is sandy, rather tropical, and prodvxces much vegetation. It 

 is remarkable that none of these specimens belongs to the essen- 

 tially spotted-colovu' variety, but ends in the partly cross-barred type. 



The evolution of the dorsal pattern proceeds as follows : — They 

 stai^t with 6 to 8 pale stripes and black-brown fields. Pale, light- 

 brown spots in one or two rows appear in all the fields, proceeding 

 from behind forwards. Against the inside of the third pair of 

 stripes appears a double series of blackish spots. Stiipes 2 and 3 

 become dull, and within each of these stripes appear, or remain, 

 white spots. The field-spots become pale, buff or whitish, and 

 then they become transversely confluent within each field. Ulti- 

 mately alternate black and whitish cross-bars are produced, which, 

 reaching from the flank through stripe 1, through field I., through 

 stripe 2, cause a cross-barred appearance. This procedure much 

 resembles that of the typical G. mexicanus. 



23* 



