COLUBER CANUS.
the form of a cross, and the under parts with transverse blotches of the latter
colour, either at the extremities of the plates, or towards their centres, or at
both. In some specimens the spots are disposed in four regular rows; in
others they are in two rows, one on each side, and each spot shaped like a
sand glass, being narrow in the middle, and widest at the extremities.
F orm, ,v c .—Figure subfusiform, and somewhat quadrangular in young and
middle-aged individualssubcylindrical in adults; head quadrangular,
rather small, posteriorly as wide as the neck, anteriorly narrow, and terminating
in an obtuse point; side of head behind eye convex; portion
of the side in front of eye flat and perpendicular. Gape rather large,
and the angles of the mouth considerably behind the eyes. From the head
the body gradually increases in thickness till it reaches its extreme, which is
generally about midway between the nose and anus ; from that point it gradually
decreases towards the tail, which is in most specimens thicker and
shorter, in proportion to the total length, than in the majority of reptiles of
this genus. The point of the tail, particularly in adult specimens, is commonly
blunt and rounded. The plates covering the upper surface of the head,
including the labial, a portion of which is so reflected as to cover the anterior
extremity of nose, are ten in number, viz. 1 labial, 2 nasal, 2 frontal, 2
supra-ocular, 1 vertical, and 2 occipital plates; the labial at its base,
which constitutes a portion of the edge of upper lip is notched, the notch
being a curve, the convexity of which is directed upwards; the shape of this
plate is triangular, its apex reaching the point at which the nasal plates come
in contact anteriorly ; the vertical plate somewhat triangular, and more or less
distinctly six-sided ; its apex lying between the occipital plates; labial plates
of upper lip six or seven, those towards angles of mouth largest, of lower lip
eleven or twelve, exclusive of the central one, covering the apex of the lower
jaw ; postocular plates generally two, anti-ocular plates one or two. Eyes
small and deeply set; nostrils small, widest behind, pointed in front, and
situated much nearer to the point of the nose than the eye. Scales of the
body rhomboidal and disposed in rows, which run obliquely across the body
from the abdominal plates on one side to those of the other, each row
generally consisting of twenty-seven scales; subcaudal scales six-sided, the
two central sides longest ; the tip of the tail usually covered with a hard
elastic, and somewhat horny sheath, the apex of which is either blunt or
aculeated. The abdominal plates vary in number in different specimens,
ranging from 172 to 209 ; the subcaudal scales from 60 to 84, and there is
no reason for supposing that the number is in proportion to the size of the
specimen. The usual length of an adult specimen is from five to six feet, but
individuals are frequently obtained which measure even more than seven feet.