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enlarged, spinose scales irregularly scattered on the back ; ventral scales 
generally smaller than the dorsals, smooth. A feeble nuchal crest, continued 
on the anterior half of the body, then gradually lost, and reappearing on 
the tail, where it is very strongly developed. Caudal scales not forming 
distinct whorls, rather feebly keeled, some denticulated or mucronate. 
Scales on upper surface of tibia moderately large and subequal, strongly 
keeled. 
A single series of large preanal pores ; two series in one specimen. 
The female could be easily mistaken for A. atra, with which it agrees in 
the shape and strong depression of the head * and in the proportions of 
the body and limbs ; the tail is feebly or scarcely compressed and longer than 
head and body. 
The scaling differs from that of the male in the following unimportant 
points: 11 scales from one superciliary to the other; 11 to 13 upper 
labials; scales on back and sides distinctly keeled, none enlarged; crest 
merely indicated on the nape, absent on the back and tail; 125 scales round 
middle of body. 
In some of the specimens the spines on the plantar and subdigital scales 
are dark at the tip. 
Greyish above, with the vertebral region lighter, yellowish, and faint 
traces of 4 or 5 darker blotches on each side of the back, which is speckled 
with black ; the enlarged scales (male) whitish ; head with dark wavy lines; 
a curved blackish line, or a blotch, along each side of the nape in males ; 
upper surface of tail with dark transverse blotches. Whitish beneath, 
sometimes with dark bluish vermiculations, the middle of the throat blue ; 
a wide-meshed blackish network on the head, more distinct in males, or 
males with the throat cobalt blue with black wavy longitudinal lines. 
The following details regarding the colours in life have been supplied 
by Capt. J. B. Knobel, who collected the specimens, and after whom this 
new variety is named : 
" They can change their colour like chameleons. I have killed one of 
various fiery-tan or terra-cotta and grey mixtures when lying on a stone, 
and when I took it from my pocket later it was dark blue and lighter blue. 
Some are dark ultramarine blue on the head and throat, Oxford blue on the 
chest and belly, and Cambridge blue on the flanks. At other times the 
whole head and body are very deep blue." 
Measurements (in millimetres) : 
1 2 
? 
From snout to vent . . . . . 126 108 
Head 28 24 
* More convex in one of the specimens examined, the length, width and depth 
being 21, 15 and 13 mm. respectively, instead of 24, 24 and 13. 
