138 OP HID I A. 



There are twelve or thirteen lower labials ; the fifth or sixth the 

 largest, and the six posterior ones very much reduced in size. 



The dorsal scales are elliptical, disposed upon twenty-nine to thirty- 

 one longitudinal series, the outer three series being perfectly smooth, 

 whilst a slight carination may be observed upon the fourth and fifth 

 series. The carinae on the remaining series are not very conspicuous. 



The tail is conical and tapering. The abdominal scutellae are 

 numerous, from two hundred and nine to two hundred and fifteen, 

 the preanal one being entire. The subcaudal scutellae range between 

 fifty-six and seventy-two, and are disposed upon a double series. 



The ground color is yellowish, with a dorsal series of subquadrate 

 blotches, about ninety in number, twenty of which are on the tail. 

 These are deep-brown, margined with black anteriorly, entirely black 

 posteriorly ; these blotches cover transversely eight or nine rows of 

 scales, embracing longitudinally five to seven scales on the anterior 

 region of the body, and two or three posteriorly. The spaces between 

 the blotches are of the uniform width of one scale for the whole length 

 of the body, decidedly narrower than in other species. A lateral series 

 of blotches on each side of the medial, covering three rows of scales, 

 and alternating with the medial series. A series of blotches along 

 the middle of the flanks opposite to the blotches of the medial series 

 of the back. On the anterior part of the body the lateral blotches 

 are elongated, and occasionally combine into a band or vitta behind 

 the neck. On the anterior third of the body, an indistinct series of 

 black spots may be seen, between the scutellae and the outer series of 

 lateral blotches. Inferior surface of head and abdomen dull yellowish- 

 white, with two series of distant blotches, the outer series more con- 

 spicuous than the inner one, and extending to the tip Of the tail. 



In the young, the middle region of the abdomen is unicolor, and the 

 external series of spots only exists, which, together with the series on 

 the middle of the flanks, are most conspicuous. 



Loc. Specimens of this species were collected in Washington 

 Territory, as far north as Puget Sound, the largest of which measures 

 nearly forty-two inches. 



Plate IX, fig. 1, represents Pituoplds tcilkesi, size of life. 

 Fig. 2, is a profile view of the head. 

 Fig. 3, a front view of the same. 



