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Show 370 DR. H. GADOW ON EVOLUTION [Mar. 20, white and black cross-bars on the flanks. The stripes prevail on the neck, shoulder, and mid-back, while spots become predominant on the rump. To such specimens applies the name of C. gracilis B. & G * The next question is whether the white colour becomes prevalent and represents the ground-colour, with black spots and lines; and this condition leads to an extreme in which the white groundcolour turns to dull or brownish, interspersed writh black spots only, which ultimately may be counted in transverse or in longitudinal rows (C. rubidus, text-fig. 70 E, see p. 293). Or, the black becomes prevalent; and this condition leads to various appearances, namely, dark-coloured wThite-spotted (leopards), or with a transverse black and white gridiron pattern on the rump, or black and wdiite cross-barred on rump and flanks (tigers). Such leopards, gridirons, or tigers, as the case may be (e. g. C. tigris of Baird & Gir., and also of Cope, Proc. A m . Phil. Soc. 1886, p. 283), occur in the Sonoran zone on the open desert, sometimes together with the Leopard-lizard Crotaphytus wisliceni, as pointed out by Merriam, quoted by Cope, p. 578. They are also common in the Mojave desert; in Utah, and in Nevada on Juniper Mountain up to 6500 ft. These spotted and barred individuals represent one kind of desert form ; another kind is C. rubidus, in which the whole dorsal surface has become uniform light brown, interspersed with black spots. These spots again may become evanescent from neck and shoulders backwards; such specimens are recorded from S. Margarita Island, Lower California. It would be interesting to ascertain to what extent the more striped individuals coincide in their habitat with those districts which are decidedly not deserts, e. g., the neighbourhood of Laredo from El Paso to S. Antonio in N e w Mexico, Fresno, Bernalillo and Los Angeles in California. CNEMIDOPHORUS MULTISCUTATUS Cope, based upon four specimens from Cedros Island, West Coast of Lower California, can scarcely claim distinctive rank. Cope gives the following data:-Length 85 m m . Humerus with 7-8 rows, but he adds that this number is not quite constant, one specimen having but 6 rows. Femoral rows 8-9, but I fail to count even 8 in Cope's figure. Pores 20-22. Throat and collar with transverse black spots and bands; tail with black spots below; "belly black and light olive mixed." Dorsal coloration like that of the C. gracilis stage of C. tessellatus. He adds that he caught a specimen structurally exactly like this multiscutatus near Pyramid Lake in Western Nevada, This, coupled with the fact that Cope himself records four specimens of * To none of these stages applies C. guttatus Hallowell, as Cope would have it. Hallowell distinctly states that the subgular fold is margined with a row of large smooth scales. |