39 



TROPIDONOTUS RIGIDUS.— %. 



Plate X. 



Characters. Body above, brown; abdomen brownish-yellow; each plate with 

 two oblong dark spots near the centre, so disposed as to make two longitudinal 

 lines. Ph 133. Sc. 51. 



Stnontmes. Coluber rigidus, Say, Journ. Acad. Nat. Scien. Philad., vol. iv. p. 239. 

 Coluber rigidus, Harlan, Med. and Phys. Res., p. IIS. 



Description. The head is sub-oval, with a rounded snout. The vertical plate 

 is hexagonal and large, broadest before, and acute-angled behind. The superior 

 orbital are oblong, quadrilateral, broader behind, and projecting over the eye. 

 The occipital plates are pentagonal and large. There are two temporal plates, 

 of which the anterior is larger. The frontal are hexagonal and descend to a 

 single square loral plate. The anterior frontal are small and trigonal, a little 

 truncated in front. The rostral plate is rather small, pentagonal, and concave 

 below. There are two nasal plates, quadrilateral, the one concave behind, and 

 the other before, for the nostril. There are two anterior orbital plates, of which 

 the superior is larger, and two posterior, small and quadrilateral. The inferior 

 portion of the orbit is completed by the third and fourth labial plates, of which 

 there are seven, large and mostly quadrilateral. 



The nostrils are near the snout, lateral, but open upwards and outwards. The 

 eyes are large, the pupil black, and iris reddish-grey. The neck is contracted. 

 The body is rather slender, and covered above with hexagonal, strongly carinated 



