HETERODON. 59 



B. Azygos plate hehi.nd the rostral separated from the frontah hy 

 small jilatcs. 



5. Heterodoii siuius, Holbr. — Vertical plate as broad as long, 

 much longer tlian the occipitals. Rostral broad and high. Azygos encir- 

 cled by five or eight small plates. Mouth very short. Dorsal rows 25, the 

 three or four externals smooth. Dorsal series of 35 blotches, with one to 

 three other series on each side. Abdomen yellowish, scarcely maculated. 

 A narrow black band across the forehead in front of the vertical, and pass- 

 ing through the eye across one labial to the angle of the mouth. 



Stn. Coluber simus, Linn. Syst. Nat. ed. xii, I, 1766, 216. — Gm. Linn. 

 Syst. Nat. ed. xiii, I, iii, 1788, 1086. 



JTeterocIon simus, Holbr. N. Amer Herp. IV, 1842, 57. PI. xv. 



Heterodon plalyrhinos, Schl. Ess. Phys. Serp. Part, descr. 1837, 97. PI. 

 iii, figs. 20-22. 



? Vipera capite viperrens, Catesb. Nat. Hist. Carol. II, 1743, 56. Tab. IvL 



Hog-nose Snake. 



Vertical plate sublieptagonal, sometimes nearly triangular ; with 

 three sides anteriorly, the lateral against the postfrontals, the middle 

 against the azygos plates, the sides very obtusely angled. Superci- 

 liaries rather short, broad. Occipitals very short, almost as long as 

 broad. Postfrontals moderate, the exterior angle scarcely reaching 

 the angle of the loral; the two separated by three small plates pos- 

 terior to the azygos. Anterior frontals not much smaller. Azygos 

 plate resting anteriorly against the rostral, and touched by the inner 

 angle of the prefrontal : there is a small plate on each side, between 

 it and the notch at the junction of the anterior and postfrontals, 

 while behind, the space between it, the postfrontals, and the vertical 

 is occupied by the three small plates already mentioned. This 

 azygos is thus surrounded on the sides and posteriorly by five small 

 plates, (this number is sometimes greater). Rostral broad and high, 

 much recurved. Eyes moderate, situated posterior to the centre of im- 

 aginary line connecting the last labial and rostral, which would pass 

 nearly through its centre. Loral subtriangular, acute above, scarcely 

 reaching to the exterior angle of the postfrontal, a small plate some- 

 times intervening. Nasal plates rather short and high ; nostril oc- 

 cupying most of the posterior one, its infero-anterior wall constituted 

 by the first labial, its lower by a small plate. Labials 7 above ; in- 

 creasing very rapidly from the diminutive first; 5th and Cth largest; 



