44 BULLETIN 17 5, UNITED STATES NATIONAL MUSEUM 



A series of large dark spots is found on the dorsum. These number 

 21 to 25 on the body and 7 to 10 on the tail. They are usually quad- 

 rangular anteriorly, although sometimes ovoid or saddle-shaped; are 

 generally more or less saddle-shaped, and frequently confluent at the 

 sides, in the middle of the body; become quadrangular anterior to the 

 vent; and appear as bars on the tail. In color they are gray anteriorly 

 and reddish brown outlined with black on the middle and posterior 

 parts of the dorsum and on the tail. They vary from 5 to 12 scales 

 in length and from 10 to 13 scales in width and are separated by mter- 

 spaces at least 5 scales, and generally more, in width. On each side 

 two or three series of smaller spots, gray or black anteriorly, and brown 

 outlined with black posteriorly, alternate with one another and with 

 the dorsal spots, the rows being somewhat irregular and more or less 

 confluent with one another and with the median spots. The ground 

 color is yellowish white. Many of or all the light scales of the sides 

 and interspaces, at least on the anterior part of the trunk, bear each a 

 central black spot. The white belly may have the anterior half im- 

 maculate, and the posterior half and under side of the tail bearing a 

 series of small brownish spots, 1 or 2 scales each in length, and 2 to 4 

 scales apart, on each side of the ventral scutes; or may have the 

 lateral series of spots present throughout the entire length of the 

 body, with additional small or minute spots scattered irregularly 

 between the lateral series. The head is pale brown, darkest on top, 

 and the throat is white. (Figs. 24, 25.) 



Variation. — Since all the specimens known of this form, with the 

 exception of the mutilated type, are from the same locahty, no study 

 of geographic variation can be made; and in such a small series, in 

 which only one of the eight specimens is a female, a consideration of 

 sexual dimorphism is equally impossible. It is perhaps significant, 

 however, that the single female specimen has only 52 caudals, as 

 compared with 61 to 66 in the male specimens, and that, in correlation 

 with this, the tail length is 0.120 of the total length, while it varies 

 from 0.136 to 0.141 in the males. Furthermore, the female has a 

 dorsal scale formula of 29-31-22, equaled in only one of the males, 

 which has a formula of 31-31-23. It will be noted that in these three 

 characters the tendencies in sexual variation correspond with those 

 found in all other forms of the genus. 



Range. — The only localities from which specimens are known are 

 Buena Vista (probably in Coahuila), Mexico, and Miquihuana, 

 Tamaulipas, Mexico. 



Habits and habitat. — Apparently there is no published record of the 

 habits or habitat of this form. They would, however, doubtless agree 

 closely with those of the allied form, d. deppei. 



Ajginities. — The color pattern and scale characters of this form all 

 indicate that it is very closely related to deppei, and although at 



