342 BR. H. GADOW ON EVOLUTION [Mar. 20, 



In opposition to the essentially spotted variety of G. communis, 

 the Ixtlan specimens retain a fair amount of their stripes. For 

 instance, in the largest specimen the fourth pair is still retained ; 

 but the first and second stripes are mostly dissolved into white 

 spots, in the way characteristic of C. communis. 



The throat is white, sometimes pink, or even with a strong- 

 brick- reddish tinge ; collar whitish ; body in the adult chequered, 

 especially on the flanks. The thigh- stripe breaks up early. Tail 

 beneath either reddish or bluish. 



Sierra de Nayarete. — Dr. Buller collected the five specimens in 

 Ranchos, in the walls of corrals, on the eastern side of the Sierra, 

 at an altitude of about 4600 feet, apparently in open, treeless 

 surroundings. These are the specimens referred to in my paper 

 (Proc. Roy. Soc. 1903, p. 118) under C. bocourti, and as aberrantly 

 coloured ; but they belong undovibtedly to the C. communis. 

 Supraoculars 4 ; collar composed of large scales ; forearm with 

 typical scutes. 



There is much individual variation in these few, probably all 

 adult, specimens : — 



85 mm. Stripes 1 and 2 broad and conspicuous, white ; 

 stripe 3 narrow and complete ; 4th pair narrow, somewhat 

 zigzag, enclosing a black centre-field. The fields are black- 

 brown, with very faint red-brown spots. There is an extra 

 white line below stripe 1, extending from the ear towards 

 the thigh ! Throat and collar pale, yellowish, with dusky 

 mottling ! Chest and belly still yellow. Tail bluish beneath, 

 93 mm. Stripe 1 is nearly gone ; stripes 2 and 3 are being- 

 dissolved into whitish spots ; the 4th pair is still complete. 

 Fields with large round yellow-brown spots in double rows. 

 Throat and collar j^ellow, much mottled with black ! Cliest, 

 belly, preanal region, and thighs yellow, chequered with black. 



97 mm. Stripe 1 is lost, str-ipe 2 much broken up ; stripes 3 

 and 4 still present. Large pale brown spots in the fields. 

 Throat and collar mottled black and yellow ! Rest of under 

 parts with much black and blue pigment, chequered with 

 yellow. Tail bluish black. 



98 mm. Stripes 1 and 2 are quite gone ; only narrow traces 

 of the others. With about 10 rows of large round yellow 

 spots on a uniformly black ground. Under parts like the 

 97 mm. specimen. 



98 mm. The 6 stripes are still well preserved, but getting 

 dissolved into white spots. Two rows of pale spots in the 

 blackish first and second fields. The broad, unicolovired 

 mid-field is bordered by black dots. General ground-colour 

 olive-grey. Throat and collar yellowish white. Chest and 

 belly much pigmented with black and blue. Tail red. — This 

 male specimen was caught at a diflierent rancho, and it is 

 distinguishable from the previous four specimens by the 

 presence of a frenocular, a very unimportant character. 



Presidio, south-east of Mazatlan in Sinaloa. — Presumably the 



