ZooL.— Vol. IV] VAN DEN BURGH— ANN I ELLA 43 



 



3. Frontal twice as broad as long. 



4. Anterior supraocular nearly as broad as its distance 



from its fellow. 



5. Interparietal and occipital divided (anomalously?) by 



a lontifitudinal suture. 



6. Six upper labials, etc. 



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. 



I will now consider these characters in connection with 

 variations found in a series of specimens of A. pulchni and 

 A. nigra. 



1. The shape of the head and snout is subject to some 

 variation in both A. pulckra and A. nigra. Unless the differ- 

 ence 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 inter- 

 parietal and occipital as frontoparietal and interparietal, 

 respectively. The former plate is not completely divided in 



