43 



TRIGONOCEPH ALUS ATRO-FUSCUS.— Troost. 



Plate IX. 



Characters. Head large, sub-triangular, broad behind, smaller and truncated 

 in front, covered with plates to the occiput, behind which are small, smooth, 

 hexagonal scales; a deep pit between the eye and nostril; upper jaw armed with 

 fangs; body above dusky, variegated with dark brown spots. PI. 133. Caud. PI. 

 at basis, 25. Sc. 18 at apex. 



Synontmes. Toxicophis atro-fuscus, Troost, Ann. Lye. Nat. Hist. N. Y., vol. iii. p. 181. 



Description. The head is large, broad behind, narrow and truncated anteriorly. 

 The vertical plate is irregularly pentagonal, with curvated sides, and an acute 

 angle behind; the superior orbital are large, and project over the eye, and are 

 irregularly hexagonal, rounded externally; there are four occipital plates, the two 

 anterior large, pentagonal, with rounded sides and very acute angles forward; the 

 posterior smaller, quadrilateral, and irregularly rounded; the frontal plates are 

 more or less pentagonal, approaching the hexagonal form; the anterior frontal are 

 smaller, and somewhat trapezoidal, with curved margins; the rostral is irregularly 

 hexagonal, with curved margins, broader below, narrower above. There are two 

 nasal plates, trapezoidal, one most incurvated before, and the other most so 

 behind, for the nostrils. Of the two anterior orbital plates, the upper is oblong- 

 quadrilateral, the posterior part concave; the inferior is triangular, its apex to the 

 orbit, and its base forming part of the pit between the eye and nostril, which is 

 completed by the second and third labial, and a small plate that rests on the third 

 labial; the inferior orbital plate is single, long, narrow; there are three posterior 



