TEIID LIZARDS OF THE GENUS CNEMIDOPHORUS 169 



which is actually the intervening form. The species, s'tejnegcri, fared 

 even worse at the hands of Gadow (1906, p. 369), for he considered 

 it a synonym of tcssellatus. 



In connection with her studies of Californian specimens, Atsatt 

 (1913, p. 39) examined the series of whiptails in the collection of 

 the Museum of Vertebrate Zoolooy of the University of California. 

 (These same specimens have been examined b}^ the wi'iter.) Her 

 conclusions Avere as follows: " One of the distinctions between t'tgris 

 and stejnegeH is based on scalation, on the relative size of the central 

 irular and collar scales. Since these appear to vary with ajje, com- 

 parison has to be made Avith specimens accurately agreein<>; in size 

 and there is no structural criterion of age or relative development. 

 Under such circumstances within any given group of material of 

 either species one finds variation in relative proportions — such wide 

 variation as to make the specific determinations extremely difficult. 

 The other distinction is based on the gray suffusion and the clearness 

 of the pattern on the sides of the head, neck and gular region. 

 G. tigris from Nevada in the Museum collection presents both dis- 

 tinct and indistinct markings on the sides of the head, Avhile the 

 specimens from Mecca, California, have distinct markings and 

 those from the Colorado River have generally indistinct mark- 

 ings. * * * On a general survey of masses of material one feels 

 that the effect of the environment upon the individual has been 

 great." 



Thus, once again not only a demonstration of the Aveakness of 

 the distinctions, but also a suggestion of the environmental nature 

 of the differences betAveen these lizards, Avas brought out. The futil- 

 ity of recognizing them as distinct species Avas realized by Camp 

 (1916, p. 71) who Avrote that " The difficulty of separating tigris and 

 stejnegeid comes from the fact that stejnegeri on the desert borders 

 of its range gradually takes on the dusky suffusion of tigris, and that 

 many examples of tigris, eA'en from the interior desert regions, liaA^e 

 fully as large central gular scales as the majority of stejnegeri. 



" Because of the practical impossibility of separating tigris and 

 stejnegeri at certain points on the desert divides and farther east in 

 southern California, the Avriter believes that the forms in question 

 had best be placed together as subspecies." 



In this way stejnegeri Avas again reduced to subspecific rank, from 

 whence it had been removed by Van Denburgh, its describer. 



The whiptails under discussion as widulatus AA'ere, on account of 

 preoccupation by C. undulatios Wiegmann (1834), giA-en the name 

 '''' mundus ''"' by Camp (1916«, p. 71), who found that they w^ere very 

 hard to separate from tigiis and stejnegeri. Therefore, mundus Avas 

 made a subspecies of tigris. 

 2306—31 12 



