REPTILES OF MASSACHUSETTS. 231 



HETERODON. Palisot de Beauvais. 



Generic 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. 



H. platirhinos. Latreille. 



Daud. Hist. Nat. des Kept. torn. vii. p. 153. 

 Karl. Med. and Phys. Res. p. 120. 

 N. H. Herpetol. vol. ii. p. 97, et fig. 



I have never seen a specimen of this animal ; but Dr. Hoi- 

 brook assures me he possesses an individual which was cap- 

 tured at Medfield. His description therefore is here intro- 

 duced : " 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 ante- 

 rior arid on the vertex. The vertical plate is regularly penta- 

 gonal, with its broadest point directed forwards. The supe- 

 rior orbital are quadilateral, elongated, and broadest posteriorly, 

 with their outer margins projecting over the eye, which gives 

 a sinister look to the animal. The occipital plates are rhom- 

 boidal. The frontal are quadrilateral, with their anterior infe- 

 rior angles very much prolonged ; the anterior frontal are 

 triangular, with their bases directed inwards, and their apices 

 rounded, and turned to the nostrils. Between these frontals, 

 so as to prevent them coming in contact with each other, is a 

 narrow elongated azygos plate, reaching from the posterior 

 frontal to the rostral plate, with a ridge on its upper surface, 

 continuous with that of the rostral plate. The rostral plate 

 is triangular, with its basis below and the apex very pointed 

 above, and recurved; with a strong carina or ridge on the upper 

 surface. The nostril plates are two on each side ; the anteri- 

 ly quadrilateral, lunated on the posterior margin, with its ante- 

 rior and inferior angle greatly prolonged ; the posterior is nar- 

 row, and concave in front to complete the nostril. There are 

 twelve orbital plates, the superior of which have been already 

 described. Besides these there are three anterior orbital plates, 



