110 BULLETIN 15 4, UNITED STATES NATIONAL MUSEUM 



Cnenvldoplioraa iiiexlcanus halsas was described by Gadow (1J)()(5), 

 He stated that balsas is a case of isolation, and is restricted to the 

 Basin of the Balsas River in southern Mexico. " This is bounded 

 on the north by an impassable barrier of high mountains, the south- 

 ern fringe of the central plateau, and on the south by the Sierra 

 Madre del Sur, the low pass of which, at Los Cajones, these lizards 

 just manage to cross, but they do not descend beyond into the coastal 

 region." The present work presents records which indicate a con- 

 tinuous distribution of these lizards throughout most of Mexico, and 

 while the}^ are no doubt restricted by high altitudes, as are other 

 reptiles, a topograpliic map of the region surrounding the Balsas 

 Basin shows an abundance of natural entrances to the place. Speci- 

 mens of gidaris have been secured south of Colima and, although 

 perhaps avoiding the coast as indicated by Gadow, they no doubt 

 range southward along the foothills of the mountains to the point 

 where the Balsas River itself cuts through the Sierra Madre del Sur 

 to flow to the Pacific Ocean. The presence of these lizards in the 

 Balsas Basin indicates that they are able to ascend to higher levels 

 from tliis point. An opening to the Basin seems to be evident from 

 the east and north through Puebla, Hidalgo, and Queretaro to 

 Guanajuato, and another, perhaps, directly from the north through 

 the state of Mexico. Although not extending to the coast at Los 

 Cajones, the form may occur along the foothills southward toward 

 Oaxaca and Chiapas, thus giving another natural migration route. 

 Therefore, it is doubtful if hahas can be " a case of isolation." The 

 subspecies itself was diagnosed as having a strong collar, scutes on 

 the forearm, and a less pronounced, more incipient tiger-pattern 

 than typlca in Oaxaca. Since there is nothing constantly definitive 

 in these characteristics, halsas is not recognized here. 



V. The forms from uncertain localities are two, costatus and 

 sealous. The first of these, costatus, was described by Cope (1877, 

 p. 95) from " Mexico " and has scarcely been mentioned since. It 

 ATas said to have " no trace of stripes, the sides being broAvn, with 

 black crossbars which join across the middle line in the lumbar 

 region." An examination of the type shows that it is merely an old 

 specimen of (fiilar'is-. 



The second form, ,'iea/oihs, was mentioned by name only as a sub- 

 species of {/vlaris by Cope in 1892 while discussing pattern evolution 

 in OneTiiidophonis. It is presumed that he intended to describe the 

 form at a later date, as he did for scahuis and setnifasckdus^ which 

 also appeared as nomina nuda at first. 



Diagnosis. — The spotted race runner may usually be distinguished 

 by the presence of a bluish ventral siiliiision. When lined, there are 

 four to eight stripes and the third (often ui)per lateral) pair on each 

 side are usually placed closer to the stripes l)elow them than to each 



