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Show 312 DR. H. GADOW ox EVOLUTION [Mar. 20, The amplitude of variation I have found, in 100 specimens, to extend from 14 to 22, but the solitary case of 14 was quite exceptional, it being associated with 16 on the other leg ; and 22 likewise occurred once only, being coupled with 21 on the other side 15/15 occurred twice, 15/16 twice, 16/16 four times, 21/21 only two or three times. The usual numbers are 17 and 18. The specimens from Tierra Colorada possess the highest number, average mean 18'8 ; those of the Pacific side of Guerrero have the smallest number, average 1 6 % and this smallest number coincides with the lowest number of femoral scales, lne Balsas specimens take up a middle position, with 175 as their mean The appended table refers only to such localities in which sufficient material was collected. It also shows that the right and left sides are practically equal. Tequesixtlan. 7 18 specimens. ) Tierra Colorada ) 23 specimens. ) Rio Balsas. 7 25 specimens. ) Coast to S. Luis. ) 19 specimens. j Total number of Pores. A light 333 „ 434 „ 442 „ 324 Left 337 „ 429 „ 437 „ 311 Mean 18'6 Pores. „ 18-8 „ » 17"5 „ 16"2 1533 1514 17 or 18 Length of hind limb.-The claw of the fourth toe usually reaches the ear, but sometimes it falls a little short of it. Throat (text-fig. 65 C, E).-Some of the granular scales covering the upper half of the throat are, as a rule, slightly larger in the centre than nearer the sides ; occasionally they are large enough to form an ill-defined little cluster, which, however, is rarely so conspicuous as it is in many specimens of C. immutabilis (text-fig- 65 A ). The Collar (text-fig. 65 C, E ) varies much in composition. In the majority, one or more rows of the large scales extend right across, while in C immutabilis the large scales are mostly confined to the middle third, becoming considerably smaller towards the sides. The presence or absence of tiny granules on the posterior border of the collar is no criterion whatever in any species of Cnemidophorus. They are either absent, or here and there one is intercalated between the scales, or they form a single, or even several complete rows of granules. Lastly, it is to be noted that this character is often clue solely to the shrinking of the soft granular fold in spirit-specimens. Coloration (text-fig. 66 ; text-figs. 71 & 72).-The variations in colour and pattern extend far beyond the limits which I was able to describe in m y first paper. The range of white or pale longitudinal stripes extends from 6 to 11 ; and the whole of the under parts, from the jaws to the anal region, varies in adidt from uniformly silver-white to deep black. It is important to |