TEIID LIZ.VTIDS OF THE GENUS CNEMIDOPHORUS 221 



Sleviii, Oil several occtisioiis, observed it running- ou its hind feet 

 only, the front feet being held clear of the ground and the body 

 raised at an angle. One was found, under a pile of brush, holding 

 in its mouth a Verticaria {C. hyiyerythrus hijpenjthms) whose 

 skull had been crushed in its powerful jaws." 



Enemies. — According to Van Denburgh (192-2, p. 508) one of 

 these lizards Avas removed from the stomach of a red racer, Mastl- 

 cophls -fiageJlwii frenatus. 



Affinities. — Gadow (1906, p. 371) expressed his idea of the relation- 

 ship of the giant whiptail as follows : " Apparently these specimens 

 from the southern part of Lower California constitute a large, 

 coarsely marbled race of O. tessellatits.^^ The writer agrees, in gen- 

 eral, with this conclusion, since representatives of the two forms are 

 geographically adjacent and scutellatioiially indistinguishable. 

 Moreover, derivation from the small, well differentiated hyperythrus, 

 the only other form of Cnemidophoms that occurs in the region, 

 seems very unlikely. A discussion of the possible origin and rela- 

 tionships of maxlnvm is reserved for the summary of the tessellatus 

 group (p. 221) and for the general discussion of relationships at the 

 end of this work (p. 251). 



SUMMARY OF THE TESSELLATUS GROUP 



The tessellatus group is confined to western North America as 

 shown in Figure 30. The various forms of this natural unit, al- 

 though differing in the maximum size attained, are remarkably uni- 

 form in other proportional features and in scutellation. None of 

 the forms has the narrow lateral longitudinal stripes characteristi- 

 cally shown by the young of the sexUneatus group. 



The tessellatus group is composed of 9 forms, 3 mainland repre- 

 sentatives, tessellatus, ruhidus, and 7naxwius, and 6 island deriva- 

 tives, celeHpes, niartyns, canus, hacatus, catalinenms, and cer'alhensis. 

 In the selection of the ancestral form of the group, the insular sub- 

 species, all of which are obviously derived from modern mainland 

 types, may be discarded. This leaves only the 3 forms, rubidus, 

 maximum, and tessellatus. The first of these, ruhidiis, now inter- 

 grades with tessellatus and occupies onl}^ a limited range just above 

 the Cape region of Lower California. Derivation of ruhidus directly 

 from viaximus of the Cape region or from hyperythims, with which 

 it is coextensively distributed, seems out of the question, but its 

 derivation from tessellatus is natural and easy. Therefore, rubidus 

 is not considered as prototypical. 



There is considerable doubt as to whether 'inaxlmus or tessellatus 

 is ancestral, although there can be little doubt of their common 

 origin. The former is confined to the Cape region of Lower Cali- 



