HETERODON. 61 



break up into small plates. The markings on the back are restricted 

 to a dorsal series, with a dusky shade opposite, and a lateral series 

 opposite the light yellowish intervals ; the ground-color of the sides 

 a quite uniform yellowish brown. Specimens from Mississippi have 

 the dorsal spot smaller and nearly circular. 



6. Ileterotlon nasicus, B. & G. — Vertical broader than long. 

 Rostral excessively broad and high. Azygos plate surrounded behind and 

 on the sides by many small plates (12-15). A second loral. Labials short 

 and excessively high. Dorsal rows of scales 23, exterior alone smooth. A 

 dorsal series of about 50 blotches, with four or five others on each side. Body 

 beneath black. A narrow white line across the middle of the superciliaries ; 

 a second behind the rostral. A broad dark patch from the eye to the angle 

 of the mouth, crossing the last two labials. 



Stn. Heterodon nasieus, B. & G., Reptiles in Stanshiiry's'Ex^l.YaXiej of 

 Great Salt Lake, 1852, 352. 



Vertical plate very broad, subhesagonal. Occipitals short. Rostral 

 very broad, high, more than in the other species, outline rounded. 

 The interval between the opposite frontals, the rostral, and the ver- 

 tical occupied by a number of small plates, from 10 to 12, or more, 

 arranged without any symmetry, on each side and behind the small 

 azygos. The base of the rostrals between the opposite anterior 

 nasals, is generally margined by these small plates, which some- 

 times, too, are seen between the vertical and the anterior portion of 

 the superciliaries. This crowding of plates causes the anterior part 

 of the forehead to be broader than in H. simus. Eye small, its 

 centre rather posterior to the middle of the imaginary line connecting 

 the tip of rostral with the lower angle of the postlabial, which 

 line scarcely crosses the eyeball. Orbital plates, 10-13 in number. 

 Loral triangular, rather longer than high, separated from the frontal 

 by a small plate. Nasals rather short, occasionally with the lower 

 part of the nostril bounded by a small plate. Labials 8 or 9 above, 

 all of them higher than long; indeed, their vertical extension is 



