43 
TRIGONOCEPHALUS ATRO-FUSCUS.— Troost. 
Plate LX. 
Cuaracters. 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. Pl. 133. Caud. PI. 
at basis, 25. Sc. 18 at apex. 
Synonymes. Toxicophis atro-fuscus, Troost, Ann. Lye. Nat. Hist. N. Y., vol. ii. 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 
uregularly 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 
