CROCODILIANS, LIZAliDS, AND SNAKES. 



775 



with symmetry on each side and behind the small azygos. The base 

 of the rostral between the opposite anterior nasals is generally mar- 

 gined by these small plates, which sometimes, too, are seen between the 

 frontal and the anterior portion of the superciliaries. This crowding 

 of plates causes the anterior part of the forehead to be broader than 

 in H. n. simus. Eye small, its center 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, 

 ten to thirteen in number. Loreal triangular, rather longer than high, 

 separated from the prefrontal by a small second loreal above it. Nasals 

 rather short, postnasal bounding the lower part of the nostril. Labials 



Tig. 168. 



HETERODON NASICU8 NASICUS BAIRD AND GiRARD. 

 = 1. 



South Dakota. 



Collection of E. D. Cope. 



eight above, all of them higher than long; indeed, their vertical exten- 

 sion is much greater than in any other species; the sixth highest, cen- 

 ter of eye over the Junction of the fifth and sixth. 



Dorsal rows of scales twenty-three, outer row smooth, rest all dis- 

 tinctly carinated, the keels extending to the ends of the scales; those 

 Just behind the parietal plates trun(;ated, with obsolete carin;v. Scales 

 on the hind part of the body rather broader and shorter than anteri- 

 orly; the inequality scarcely evident in large specimens. 



Ground color light brown or yellowish gray, with about fifty dorsal 

 blotches from head to ti]) of tail; the thirty-ninth opposite the anus. 

 These blotches are (juite small, rather longer transversely, subquad- 

 rate, or rounded, indistinctly margined with black, (obsoletely on the 

 outside) ; they cover seven to nine scales across, are two to two and 



