334 REPORT OF NATIONAL MUSEUM, 1898. 



sliades of brown, although in some (as S. malachiUcus) this region also 

 is of some shade of green or blue. 



When the animal raises the head, as it habitually does, the brilliant 

 colors of the throat are visible, but those of the sides are much less 

 apparent. All these colors are most conspicuous in the males, and in 

 many species they are absent from the females. They are to be regarded 

 as secondary sexual characters, and are i)robably visible to the females 

 at the time of copulation, since the inferior surfaces of the sexes are 

 then in juxtaposition. 



The species of Sceloporus are conspicuous objects wherever one travels 

 in the southern United States and Mexico. In the eastern district of 

 Nearctica the 8. undnlatus is seen running on fences and walls. In 

 Texas the 8. spinosus runs up trees with great activity, dodging the 

 pursuer behind branches, with good result to himself. In southern 

 Texas and in Mexico 8. torquatus is constantly seen on the vertical 

 faces of rocks that so frequently border the highways, hiding in fissures 

 from enemies, and often attracting the attention of the most careless 

 observer. Throughout Mexico the 8. micro! epidotus runs over the hori- 

 zontal rock surfaces and stone walls, where it finds concealment. So 

 the 8. scalaris haunts the soil and sand, and hides in holes that are 

 always convenient. 



Thirty-four species are known to me, and are distinguished in the 

 following analytical table. About half of them belong to Nearctica and 

 half to the Central American region of Neotropica. None are found 

 elsewhere. In Costa Eica at one extremity of the distribution there is 

 but one species {8. malachiUcus)^ and there is but one in the eastern 

 region of Nearctica (^S". undulatus). 



I. Supraocular plates separated from supraorbitals by a row of scales, and from 



snperciliaries by one or more rows of scales 

 distinct in form from the latter. 



A. Lateral scales granular. 



Femoral pores more than 10 ; head plates carinate, 

 frontal longitudinally divided ; parietals 2, can- 

 thals 2; dorsal scales moderate, uniform, 10 in a 



head lengtli ■ S. ufiformis Cope, 



Dorsal scales interrupted by smaller ones on the 



median line S. helerolepia Boulenger. 



AA. Lateral scales 8{(uamous, in longitudinal series, like the dorsals. 



Femoral ])ores more than 10 ; head plates carinate, 

 frontal single, 2 scales on can thus; light stripes 

 separated by brown spots above. 



S. scalaris Wiegmann. 

 AAA. Lateral scales squamous, in series directed upward and backward; dor- 

 sals parallel. 



B, Head plates carinate or wrinkled; frontal divided longitudinally. 



a. Femoral pores less than 10. 



P'acial scales keeled; laterals smaller than dor- 

 sals; 2canthal8; 2 parietals; colors bright. 



S. siniferus Cope. 



Facial scales keeled; laterals smaller ; 2 parietals; 



1 canthal; colors dull S. squamosus Bocourt. 



