VIPERA LACHESIS. 95 
and upper surface of the tail are of a uniform color of very dark bistre, 
approaching to black; scales on the back are shaded with the same dark 
color on the front side, and of a dirty, yellowish-light brown color on 
the back side; belly of a murky-yellowish white in the centre, tinged 
with a lead-colored shade on the sides; under side of the jaws, throat, 
and neck, covered with medium-sized scales, regularly disposed in diago- 
nal rows. 
The lowest angles of the rhomboidal macule (which approach the 
nearest to the sides of the scuta), terminate abruptly, without com- 
pleting the angle, thus leaving a break in the mark or rhomboid; 
this is inclosed by a small semi-rhomboid, the angle of which terminates 
just above the upper edges of the scuta; the periphery of these smaller 
maculz is somewhat indistinct in places. It has long, stout fangs, and 
the disposition of the buccal parts is identical with that of the Crotalus 
Jasciatus, See page 81. 
No. 3. Vipera Lachesis Niger, called Mapana fina, and 
when an individual of this variety has the tip of the tail 
terminating in a horny point, it is called Mapana de Puya 
(pua). 
Length from 3’ 6/7 to 4’ 6/7; diameter always proportionate to its 
length; head hastate, triangular, black on its upper surface, greenish- 
white on its periphery and under the throat; dorswm blackish, marked 
in angular, irregular-shaped lines, and macule on a lighter background, 
which shades down gradually into a greenish-white on the belly ; trunk 
tapers gradually towards the tail, and also towards the neck, which is 
very long and rather slender. 
Tt has fangs that are long and slim. Its movements are ex- 
ceedingly graceful and rapid; possibly, there is not another 
snake known in the world which is more aggressive or quicker 
to bite, or in its movements. 
The female when it has just given birth to its brood, if at- 
tacked or threatened, receives into its mouth the snakelets, 
which come out from their hiding-place again as soon as the 
danger has passed. This same fact is mentioned by several 
naturalists as having been observed in other varieties. 
