aa. Oue parietal. 



CROCODILIANS, LIZARDS, AND SNAKES. 337 



III. .Sui^iaocular plates only partly or not separated from supraorbitals by a row of 

 scales, auil separated I'roiu siiperciliaries bj' but few scales, 



A. Femoral pores from two to six; external supraoculars lanceolate. 



Facial scales smooth; supraoculars wide; one 

 parietal plate; two canthals; no collar, 



S. liorrhlus Wiegmann. 

 AA. Femoral pores exceedin<r 10 in number; external supraoculars squamiform. 

 a. Two parietals. 



Scales not keeled, serrate ; seven in a head length ; 

 dark, with narrow pale cross-bands ; scales with 

 small spots of various colors. 



S. orcuttil Stejneger. 

 Scales keeled, 6-7 in a head length ; parietal scales 

 wider than interparietal ; back with broad red- 

 dish longitudinal bands *S. zosteromus Cope. 



Scales keeled in thirty-two dorsal rows from head 

 to tail; a cervical black collar interrupted 

 above ; back crossbarred with brown or spotted. 

 S. clarkii Baird and Girard. 

 Scales large, carinate, seven in a head length ; pari- 

 etal plates wider than interparietal and all wider 

 than long; head yellow; muzzle black, 



S. melanorhinus Bocourt. 



Tlie ffenus Sceloporus in Nearctica belongs especially to the Sonoran 

 rey ion. jS^o species has a range exclusively outside of that region iu any 

 other part of iSTearctica, with the possible exception of a species or two 

 iu Lower California and the S. tkayerU iu southwest Texas. S. tor- 

 <iu(itns, S.spinosus, S. rariahilis, and 8. scalaris are not Sonoran species, 

 but they are Mexicans which pass over our borders. From the Sonoran 

 ceuter S. undulatus radiates in one form or another all over the conti- 

 nent south of the Canadian district. 8. graciosus ranges the whole 

 length of the Great Basin, and 8. clarMi, in its forms 8. Heidi and 8, 

 zo.steromus, into and to the end of the Lower Californian Peninsula. 

 The only possible exception to the above statement is the 8. orcuttii, 

 which is found near the coast in southern California, and with a few 

 other species of reptiles characterizes a limited district, whose distinct- 

 ness is so far uncertain. In Xearctica the distribution of this genus is 

 closely similar to that of Cnemidophoriis. 



The geographical distribution of the species, so far as now known, is 



as follows: 



I. Fauna Nkauctica. 



S. undulatua Latreille. 



a. KASTERN REGION. 



h. AUSTHORIPARIAN REGION. 



-S". idtdulatiis Latreille, >'. sphioans Wiegmanu. 



C. CENTRAL REGION. 



S. undi(J((tii8 Latreille, 5. bisvriutiis Hallowell, S. graciosus Baird and Giranl, 

 S. consohrinus Baird and (Jirard. 



(/. PACIFIC REGION. 



S. undiilatus Latieille. 



NAT MI'S 98 22 



