496 REPORT OF NATIONAL MUSEUM, 1898. 



series of three more plates (one azygoua) between them and the rostral. 

 The nostril perforates a single small nasal plate. The space between 

 this and the eye is occupied by two rows of five plates, with two other 

 rows in a line above these posteriorly. Labials either bordering orbit, 

 or more frequently separated by one or two rows of scales. Ten upper 

 labials. Ears a short longitudinal closed slit or foramen of varying 

 size in line between the mouth and lateral groove. 



There are sixteen longitudinal series of plates in the dorsal sheet, 

 the outer on each side the narrower, and ten in the ventral, the outer 

 narrower; 126 in series from head to tail. The central six rows on the 

 back have a distinct though blunt cariiiation, almost inappreciable on 

 the next rows; the rest of the lateral and all the ventral perfectly 

 smooth. Tail very long. Seven or eight i)reanal scales, a little larger 

 than the abdominal. 



The color in most specimens from the Atlantic States is a very dark, 

 greenish olive above; x)Osterior border (in the corners) of each scale, with 

 two bluish or greenish white rounded spots. The central line of each 

 series, especially where traversed by the ridge, is darker than the 

 ground color and not spotted. The under parts are plain greenish 

 white. The top and sides of the liead are spotted like the back. 



A few Atlantic specimens have the central eight or nine rows of 

 scales brownish or olivaceous yellow, the checkeis or tessellation of 

 the first variety showing through either irregularly or as transverse 

 bands of black spotted with white. In many specimens three stripes 

 above the fold on each side may be indistinctly outlined, while in otliers 

 the three stripes may be perfectly distinct. Tliese may be reduced to 

 two or even one stripe, and occasionally traces of a fourth may be 

 present. With these may or may not be associated a median dorsal 

 stripe. 



There are considerable variations in the sqiiamation of this species. 

 The most usual is that which concerns the contact of the interfronto- 

 nasal with the frontal. This contact is rarely wide, is frequently 

 narrow, and less frequently does not exist, the prefrontals being in con- 

 tact on the middle line. I exbibit this and the presence of two inter- 

 frontonasals in the following table: 



I. Oue iuterfroutonasal. 



A. Iiit(;rfroutonasal broadlj' ia coutact with frontal; Cat. No. 15537 (a), half- 



grown; Witchita River, Texas, E. D. Cope, adult. 



B. Coutact narrow; Cat. Nos. 8941, 14584, 9358 (young), adult; {2 adults); Cat. 



Nos. 14142 (2 spec); 5322, 15537 (b) adult; 12783, 13809, 4985, 9360. 



C. No contact between frontal and iuterfrontonasal; Cat. Nos. 32i)l, 20811, 9358 



(young), 15537 (c) adult; 5731 half-grown; 5130, 16949, 10584. 



II. Two intorfrontonasals, anterior and posterior. 



Anterior interfrontouasal fused with right posterior intornasal; Cat. No. 10584. 

 Anterior interfroutonasal distinct, Cat. No. 21359. 



The degree of the carination of the scales varies considerably, but it 

 is generally more conspicuous in the young than in the adult. Usually a 



