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Show 1906.] IN MEXICAN LIZARDS. 325 Thirdly, the stripes have a tendency to break up first near the root of the tail or rump, and this feature proceeds forwards. 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; but during m y 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 geographically 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. guttatus 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 lastly 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 m m . in length, from Agua fria 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 C. guttatus are known only from the open forests with dense undergrowth, or similar patches of woodland, in the State of Vera Cruz and its confines with those of Oaxaca.-It has the * Wiegmann's diagnosis, although not complete, is sufficient: " Cnemidophorus cineraceus guttis albidis in series 4 longitudinalibus dispositis, adspersus. Latera superne vitta lata, stria pallide viridi supra infraque inclusa, intense nigrescenti ; interne maculis multis pallidis adspersa. ..." 22* |