382 PROCEEDINGS OF THE NATIONAL MUSEUM you. 92 
Application of this character to occidentalis does not yield com- 
pletely satisfactory results, however, for the black tips of the mid- 
dorsal scales shade more or less gradually into a gray, stippled posterior 
portion. Nevertheless, the four characters above described (1, dorsal 
color, light spots; 2, black areas on sides of head; 3, bands under tail; 
4, individual pattern of middorsal scales) do serve to differentiate 
three races in Mexico: occidentalis, in southern Chiapas and southern 
Guatemala; margaritiferus, on Atlantic slopes from southern Texas 
into Central America; and an unnamed form described below as jistu- 
losus, occurring from the Tehuantepec area northward on Pacific slopes 
to southern Sinaloa. It is of great interest that specimens from 
Tonala, Chiapas, are neither fistulosus nor occidentalis, but typical 
margaritiferus. This distribution corresponds more or less with that 
of Sceloporus v. variabilis. It isthe only area in Mexico where typical 
margaritiferus occurs on Pacific slopes. 
In studying differences in Mexican margaritiferus I have largely 
neglected Central American specimens, some of which I realize do 
not conform to the present definition of typical margaritiferus (sub- 
caudals not uniformly black-edged). Their dorsal color prevents any 
except those from southern Guatemala from inclusion with occidentalis, 
and their separation geographically from fistulosus, as well as the 
individual scale pattern (like margaritiferus), makes unwise associa- 
tion of any specimens with that race. Pending further studies, prob- 
ably all Central American specimens (except occidentalis) should be 
referred to typical margaritiferus, with which they agree in most 
respects. 
The Mexican specimens I have examined (about 100) can be identi- 
fied easily by the accompanying key, with the exception of some 
juveniles (discolored) and of certain adult specimens from the 
Tehuantepec area, which also unfortunately are discolored by long 
preservation in formalin. Specimens thus discolored cannot always be 
definitely identified, and are best named by geographic probability. 
KEY TO MEXICAN SUBSPECIES OF DRYMOBIUS MARGARITIFERUS 
1. All or most of posterior edge of subcaudals dark or black_------_-_--__- Pe 
All or most of posterior edge of Subcaudals white (the subcaudal surface 
NMaATrked) 222 3 See Be ee ee ee eee 3 
Anterior edges of median dorsal scales blue (in adult specimens), white (faded 
specimens) or gray (young specimens), the color well differentiated from 
ablackctip of Scale= 2222S See sa 222. SS Se ee eee eee margaritiferus 
Anterior edges of median dorsal scales black, the color completely surrounding 
a dightiicentraluspota. sai fe ee a ee eee fistulosus 
3. Sides of head in temporal region no darker than general tone of dorsal surface 
of nape; light spots in centers of scales diffuse, gray-brown, stippled 
occidentalis 
bo 
