_Capite squamis lævibus, subconvexis; auribus ovalibus, margine
anteriore unidentato; squamis temporum collique rotundatis lævibus
imbricatis; colli minimis; serie unicâ squamarum supralabialium;
squamis dorsi rhomboideis, carinatis, posticè acuminatis; abdominis
squamis omnibus integris; femorum facie posteriori omninò
granulosâ._
Habitat, Port Desire. Mr. Darwin.
DESCRIPTION.—General form resembling that of _Pr. pictus_ and
_cyanogaster_. Head moderately short, obtuse, covered with rather
large slightly convex scales; a single row of scales between the
labial and the orbitar. The anterior margin of the ear has a
single tooth. The temples and the sides of the neck are covered
with imbricated scales, which have no carina—those of the neck,
especially those on the fold of the skin are smaller and more
raised than the others. The scales of the back are rather large,
rhomboidal, with a distinct carina, terminating in a point. Those
of the abdomen and sides are all of them entire at the margin. The
posterior surface of the thighs is wholly granular.
The only specimen obtained being a female, the number of pre-anal
pores is not known.
The general colour of this species is brownish grey; a black
longitudinal line runs down the middle of the back and tail. There
are two series of black spots on each side, and a small
interrupted fascia of the same colour extends from the shoulder to
the thigh. The belly is of an uniform dirty white.
_Plate 3._
[Illustration:
_From Nature by B. Waterhouse Hawkins
in Lithotint C. Hullmandel’s Patent._
]
_1. Proctotretus_ _Bibronii_ │_Nat. Size._
_2._ _tenuis_ │ „
_a & b._ _1 & 2._ _Magnified Views of Heads._
This species approaches considerably to _Pr. cyanogaster_ in general
form and habit, and in many of its characters; but it may be at once
distinguished from it not only by its colouring, but by the absence of
even the slightest appearance of a carina on any of the scales of the
temples or of the sides of the neck.
DIMENSIONS.
Inches. Lines.
Length of the head 0 6
of the body 1 6
of the tail 3 4
────────────────────────────────────────────
Total length 5 6
Length of anterior extremity 0 7
of posterior extremity 1 1
Found by Mr. Darwin at Port Desire, in Patagonia.