7. A narrow shield separates the third labial from the loreal. 8. Five lower labials. 9. Twenty-eight scales around middle of body. 10. No enlarged preanal scales. 11. Tail ending obtusely, three-eighths total length. 12. Dark gray above, with three fine black longitudinal lines; sides and lower surfaces whitish. [Footnote 17: Ann. & Mag. Nat. Hist. 5th ser. v. 20, 1887, p. 50.] I will now consider these characters in connection with variations found in a series of specimens of _A. pulchra_ and _A. nigra_. 1. The shape of the head and snout is subject to some variation in both _A. pulchra_ and _A. nigra_. Unless the difference in shape in the type of _A. texana_ is very great, one is safe in ignoring it as a basis of specific distinction. 2. One of my specimens of _A. nigra_ (Cal. Acad. Sci. No. 6255) shows a horizontal suture extending from the nostril to the second labial. Another (No. 6244) has such a suture between the nostril and the rostral plate. 3. There is considerable variation in the shape and size of the frontal plate in both _A. pulchra_ and _A. nigra_. It not infrequently is twice as broad as long (No. 6236, etc.), but may be nearly as long as broad. Sometimes it nearly touches the rostral (No. 5103). 4. The anterior supraocular is nearly as broad as the distance which separates it from its fellow in some specimens of _A. pulchra_ (No. 5110) and _A. nigra_ (Nos. 6233, 6243, 6249, etc.). In some specimens it has scarcely more than half this breadth. 5. I regard the plates which Mr. Boulenger calls interparietal and occipital as frontoparietal and interparietal, respectively. The former plate is not completely divided in any of my specimens. One example of _A. pulchra_ (No. 5110), however, has it longitudinally divided throughout the posterior third of its length. The interparietal (occipital of Mr. Boulenger) is completely divided longitudinally in one example of _A. nigra_ (No. 6228) and divided through one-fifth its length in another (No. 6218). 6. This is the normal arrangement, but is subject to variation. 7. This shield may be absent. 8. The number of lower labials ranges from five to seven. 9. The number of scales around the middle of the body varies in _A. pulchra_ from twenty-four to thirty-four, while in 54 specimens of _A. nigra_ the number is twenty-eight in 12, thirty in 36, and thirty-two in 6. 10. The preanal scales, as already stated, may be not enlarged, moderately enlarged, or twice as long as those preceding them. This is true in both _A. pulchra_ and _A. nigra_. 11. The length of the tail is subject to so much variation that it cannot be regarded as furnishing a good specific character. The longest ones I have seen are one-third the total length in _A. nigra_ and two-fifths in _A. pulchra_. 12. This is the coloration of some specimens of _A. pulchra_.