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Show 1906.] IX MEXICAN LIZARDS. 313 note that some of these variations seem to coincide with geographical districts. Rio Balsas: 34 specimens (text-fig. 71 E, F).-The general impression made by these specimens is that they are rather effacing than increasing or emphasising their stripes on the mid-region of the back. Only stripes 1 and 2 are always white, while the third pair is often thin and dull. The chief variations occur in this mid-field, which is enclosed between stripes 3-3. In the 9-striped specimens stripes 4 + 5 + 4 always form a dull field or complex. The chief variations are as follows :- (1) The space between stripes 3-3 is lined with a dull brown band on either side, enclosing a central, rather broad and green mid-stripe, which is sometimes so broad it can scarcely count as a stripe, looking rather like the pale mid-field of a 6-striped lizard. Such 6- or 7-striped specimens are represented by 1 very young, 2 adult females, 1 immature cS, and 4 large adult males. (2) This 4th or central stripe is dull or dusky, and lined on either side by a thin whitish line, the beginnings, or remnants, of stripes 4-4, and there is in most cases a central, very weak and pale 5th streak which extends from the occiput over the neck, rarely to between the shoulders. Such 8-striped specimens are represented by 2 very young examples and by 11 adult females, in only three of which the stripes 4-4 are at all w^ell defined. In one 7-striped male, 69 m m . length, the central green stripe shows a faint indication of being divided in the centre by a thin dark line ; a transitional stage from the 7- to 8-striped condition. (3) As before, but the stripes 4-4 are better marked, and the 5th, impaired streak extends from the head to the middle of the back, rarely to the rump. Such more or less completely 9-striped specimens are 6 adult females and 6 adult males. Field I. is always conspicuously black or black-brown in the females, and the lateral band or field below it is dull and inconspicuous. In the males, field I. is mostly dull ashy brown, while the lateral field inclines to brick-red, often with strikingly pretty effect. But there are no white spots in any of the fields nor in the lateral field. All the under parts of the females are white, more or less mother-of-pearl, with an occasional tinge of green or bluish towards the flanks. The under surface of the tail is white, bordered with dusky or bluish colour. In the males the under jaw, whole throat, collar, chest, and abdomen are uniform bluish black, and this extends over the preanal region, and over the under surface of the fore and hind limbs. The tail is white, bluish towrards the sides. In both sexes stripe 1 extends upon the front of the thigh, reappears on the whole of the posterior side as an unbroken white line, and is continued along the side of the tail. Tierra Colorada : 21 specimens (text-fig. 72 B), 1 from South slope of Los Cajones, and 1 from Ayutla,-This is an essentially |