42 SYNOPSES AND DESCRIPTIOICS. 



large, posterior two small. Submentals two pairs. Scales smooth, in 

 17 rows, medial narrow, outer and caudal as broad as long. Ventrals 

 175—190. Anal entire. Subcaudals 80—110 pairs. 



Uniform lustrous black above, varying to olive or leaden, more or less 

 yellow, on the western prairies; chin, throat, and portions of the labials 

 white. The white extends upward behind the jaws, or is limited to the 

 chin. 



The young are olivaceous with a dorsal series of large, darker-edged, 

 irregular-shaped brown spots, the largest of which forms a transverse 

 band immediately behind the head. Sides and abdomen with irreg- 

 ularly placed spots of brown, varying in size from that of a dot to 

 that of a couple of scales. The spots become obsolete backward. Head 

 yellowish brown above, spotted or mottled with dark, below yellowish. 

 Mississippi Valley and eastward. 



Vlir. FLAVIVENTEIS. 



Say, 1823, Long's Exp. II, 185. 



The "Blue Racer" of the prairies is rather stouter than the "Black 

 Snake" of the Eastern States. On the back it is light olive, greenish 

 or blueish ; beneath yellowish, some of the scales and interspaces showing 

 darker. The young are mottled like those of the black snake and without 

 spots below. 



var. MENTOVARIUS. 

 CoRYPHODON MENTOVARIUS Dumiril & Bihron, 1854, Erp. Gen. VII 187. 



Back greenish-brown. A single labial entering the orbit. This species 

 resembles greatly C. constrictor; it is distinguished by the single labial 

 beneath the eye. The head is comi)aratively more elongate, and the eye 

 larger. Tlie hinder submentals are longer than the anterior, which is not 

 the case in C. constrictor. (Dumcril.) Mexico. 



Coluber flagelliformis. 



II<ilhr<mk, 1830, N. A. Ilrrp., ed. I, 107, pi. XIX. 



Long, slender, with flat belly ; head distinct, elongate, narrow, subquad- 

 rangular in transverse section, as deep as wide at the eyes, crown flat, bent 

 downward slightly in front of tlie orbits ; tail long, near one fourth of total, 

 slender, tapering regularly to tlic ti]i. Eyes large, over the fourth and 



