TEIID LIZAEDS OF THE GENUS CNEMIDOPHOPtUS 157 



color is observed. Of course, in some localities there are exceptions 

 to these statements * * * but on the whole the general back- 

 ground colors of the country seem to be reflected in the coloration 

 of the reptiles." 



The desert forms to be diacussed under the first section^ designated 

 above are as follows: mela-iostethios^ variolosus, aethiops, dispar^lis, 

 esfehanetisis, jntnctilineaJis, and dicl'ersonae. 



The first of these, melanostetlms^ described by Cope (1863), Avas 

 said to have a shorter hind foot than gmcilis, and not to exhibit 

 that abrupt transition from the small posterior to the large anterior 

 gular plates shown by tessellatm and tlgrls. Also, the coloration was 

 said to be different in that melanostetlius was largely black beneath. 

 Through general study it has been found that the young of lizards 

 usually have proportionately longer hind legs than the adults. Since 

 the type of gracilis is a young specimen and that of nvelanostethus an 

 adult, the shorter hind leg in melanosfefhus is to be expected. (Data 

 showing variability in the length of the hind leg are presented below 

 on page 175 under the subject of variation). The type of transition 

 between the anterior and posterior gular scales is highly variable 

 when series are examined and may be regarded as largely an indi- 

 vidual characteristic. 



The coloration of the best developed examples of meJanostethus 

 often seems, at least superficially, diagnostic and distinctive, since 

 typically the lower surfaces are covered by a more or less continuous 

 black or dusky suffusion. Therefore, melanosfetkm, although some- 

 times " philosophically " ([uestioned, has been given general recogni- 

 tion until the present time. An examination of the types, which 

 came from the Colorado River, " California," proves them to be less 

 characteristic of what might best be called " melmiostethus " than 

 certain specimens of other regions or even of the same general area, 

 since they show a mixture of both black and white on a slaty ventral 

 surface. Such specimens may logically be regarded as intermediates 

 between the extreme dark and white ventralled phases of tessellatus, 

 but in this instance the dark phase is apparently favored. 



Van Denburgh became interested in this problem in 1890 (p. 344) 

 and wrote as follows : " I have been unable to detect any difference 

 between Cnertiidophori from southeastern Arizona and specimens of 

 tigris from Idaho and California, except that the adults from the 

 former locality have throats suffused with intense black, while in 

 tigris this region is usually grayish slate. The types of melmio- 

 stethus are more nearly like tigris than like specimens from south- 

 eastern Arizona, but their paleness may be seasonal rather than geo- 

 graphical. When more specimens have been collected it may become 

 necessary to regard melanostethus as a synonym of tigris.'''' 



