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HETERODON .—Palisot de Betmvais. 



Genus Heterodon. — Characters. Plates and scales as on the Colubri; the 

 rostral plate a trihedral pyramid, with a ridge above and pointed at the tip; 

 posterior maxillary teeth largest. 



HETERODON PLATIRHINOS. 

 Plate XXI. 



Characters. Head short, flattened, triangular, turned up and pointed at the 

 snout, a strong ridge on the rostral plate above; body grayish or yellowish-gray 

 above, with large blotches or transverse bars or oblong spots of black; abdomen 

 dirty white. PI. 144, sc. 42. 



Synonymes. Coluber heterodon, Daud., Hist. Nat. des Rept, torn. vii. p. 153, fig. of head 

 pi. lx. fig. 28. 

 Coluber heterodon, Say, Amer. Jour. Arts and Scien., vol. i. p. 261. 

 Coluber heterodon, Harl., Med. and Phys. Res., 120. 



Description. The head is large, flat, triangular, broad behind, with the snout 

 pointed and elongated at the tip; it is covered with scales on the posterior part, 

 and with plates on the anterior and on the vertex. The vertical plate is regularly 

 pentagonal, with its broadest point directed forwards. The superior orbital are 

 quadrilateral, elongated, and broadest posteriorly, with their outer margins pro- 

 Vol. II.— 13 



