Hurter — Herpetology of Missouri. 175 



The Bull Snake is oviparous, the eggs yellowish white 

 with a tough leathery shell. It is the largest snake found 

 in this state. 



Genus heterodon. 



Posterior maxillary teeth much enlarged, solid. Rostral plate very 

 high, with upturned edges, anterior face flat. An azygous plate behind 

 the rostral. Scales keeled, in twenty-five rows. Anal plate divided. 

 Subcaudals in two series. 



62. Heterodon platirhinos Latreille. Blowing Adder. 

 Spread Head. Spreading Viper. 



Heterodon tigrinus, Heterodon annulatus, Coluber thraso, Heterodon 

 platyrhinus, Coluber cacodaemon, Coluber heterodon, Anguis capito 

 viperino, Boa contortrix. 



Description.— Rostral plate triangular, point produced upwards, 

 slightly recurved, anterior margin sharp, keeled above. Azygous plate 

 elongate, bounded anteriorly by the rostral, at the sides by the inter- 

 nasals and posteriorly by the prefrontals. Internasals triangular, with 

 the apex pointing forward. Prefrontals wider than long. The azygous 

 plate extending half way between the prefrontals. Nasals two. Nostril 

 valvular, situated between the two nasals. Loral small, higher than 

 long. Orbitals nine to eleven. Temporals 3-4 or 4-4. Upper labials 

 eight, the seventh the largest. Lower labials nine to ten. Anterior 

 chin shields two. Posterior four and small. Three lower labials in 

 contact with the anterior chin shield. Head large, short and broad. 

 Snout recurved. Eyes large. Mouth cleft, large, and much curved. 

 Body stout, tail very short, tapering rapidly. Dorsal rows of scales 

 twenty-five, all distinctly keeled, with the exception of the two or 

 three outer rows, of which the first is smooth and the other two only ob- 

 scurely keeled. Ventrals 120-150. Anal divided. Subcaudals 43 to 60 

 pairs. 



Color. — Color above brown, with a dorsal series of dark quadrate 

 blotches, separated by interspaces of one or two scales. Margin be- 

 tween blotches frequently white. Smaller dark oval to round blotches 

 alternate with the dorsal. Two large black blotches on the nape. 

 Top of head brown. A dark line across the prefrontals and anteor- 

 bitals joins the anterior angles of the orbits. Another black line across 

 the superciliaries and the base of the frontals, joining the posterior 

 angle of the orbits. The snout is much lighter brown than the top of 

 the head. Upper labials yellowish, minutely dotted with dark brown 

 on the upper edge. Lower labials, chin and throat yellowish. Belly 

 greenish to yellowish, often clouded with blackish, which color often 

 predominates on the posterior part of the abdomen. Lower side of 

 tail yellow. 



Size. — Total length 780 mm.; tail 115 mm. 



