370 DR. H. GADOAV OX 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 tiie name of C. gracilis 



B. & G.* 



The next question is ivhether the white colour becomes prevalent 

 and represents the ground-colour, with black sjoots and lines ; and 

 this condition leads to an extreme in which the white ground- 

 colour turns to dull or brownish, interspersed with black spots 

 only, which ultimately may be counted in transverse or in longi- 

 tudinal rows {C. ruhidns, text-fig. 70 E, see p. 293). Or, the black 

 becomes prevalent ; and this condition leads to various appearances, 

 namely, dark -coloured white-spotted (leopards), or with a trans- 

 verse black and white gridiron pattern on the rump, or black and 

 white 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. Am. Phil. Soc. 

 1886, p. 283), occur in the Sonoi-an zone on the open desert, some- 

 times together with the Leopard-lizard Crotaphytxis loisliceni, 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. 7-ttbidus, 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 recoixled 

 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 New 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 mm. Humerus 

 with 7-8 I'ows, 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 

 midtiscutattis 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. guttatiis Hallowell, as Cope would liave it. 

 Hallowell distinctlj^ states that the subgnlar fold is margined with a row of large 

 smooth scales. 



