HETERODON. 57 



4. Ilelerodon afuiotles, B. & G. — Vertical plate longer than oc- 

 cipitals, -which are small, and as broad as long. Azjgos in contact with the 

 frontals. Rostral low, obtuse, and very little prominent. Eye more an- 

 terior. Dorsal rows 23 or 25. Outer row smooth, 2d and Sd very obso- 

 letely carinated. Scales broader, smoother, and more rounded than in n. 

 platyrliinos. Keel not extending to the tip. Black, with 18 transverse yel- 

 lowish bands on the body, and 7 on the tail ; the dark intervals much broader 

 than the light bands, sometimes entirely black. 



Vertical plate hexagonal, narrower behind, and more elongated 

 than in H. platyrliinos ; lower than the occipitals. Postfrontals large, 

 extending down to the loral. The anterior frontals rather larger 

 than in H. i-)latyrhi7ws, separated by the azygos and rostral. Rostral 

 small, moderately recurved, much smaller and less conspicuous than 

 in H. platijrhinos. Superciliaries long, narrower than in H. plcity- 

 rhinos. Scales on back of the head broad, flat, carination very obso- 

 lete. Imaginary line connecting tip of rostral, and posterior angle 

 of last upper labial passes entirely below the eye, whose centre is an- 

 terior to the middle of this line. Eye large, its centre above the 

 middle of the 4th labial. Loral nearly square, rather narrower 

 above. Nasals small, which with the less development of the rostral 

 brings the eye more forwards. Labials 7 above. Owing to a greater 

 development of the suborbital series, (of 9 plates,) the labials are 

 lower than in M. platyrJunos. The posterior upper angle of the 2d 

 labial, as well as the 3d, 4th, and anterior upper angles of the 5th, 

 are in contact with the suborbitals. The difference from H. platy- 

 rliinos in this respect is caused by the much greater size of the 2d or 

 3d labials, the first being much smaller than all the rest. 



Dorsal rows of scales 23; exterior smooth, 2d and 8d very obso- 

 letely carinated, rest of scales more so, but in all cases less distinctly 

 than in II. j^laty rhinos. The keel on each scale does not extend to 

 the tip, but becomes obsolete at a point from the tip of one-half to 

 one-fifth of the length ; while in S. jolatyrhinos it extends very 

 nearly, if not entirely to the extreme tip, especially on the back. 

 The scales also are broader and more oval. The tail is slenderer 

 and more tapering than in H. platyrliinos, and is not as thick as the 

 posterior part of the body. 



Color above lustrous pitch-black, crossed by 18 transverse light 

 yellow bands, from head to anus, and 7 on the tail ; sides mottled 

 with black and yellowish. Beneath yellowish, blotched with black. 



