a Family of Thysanura. 3795 
In spite of careful search, I have failed to discover the least 
_ trace of eyes, though Nicolet describes his species as possessing 
six very small eyes on each side of the head, placed in two rows. 
Neither Westwood nor Gervais seem to have observed eyes on 
their specimens, which, however, probably were specifically dif- 
ferent from those of Nicolet. 
The occiput is along the middle divided by a fine, closely 
and minutely dentate suture, which is observed also along the 
dorsal shields of the thorax-rings. In the centre of the head 
the seam bifurcates; and the branches form the boundary be- 
tween the occiput and the forehead, with the points of insertion 
of the antenne. 
The prothorax is considerably smaller than either the meso- 
thorax or metathorax, which latter are of about equal size. 
The transverse folds which separate the dorsal shields are not 
chitinized in Campodea as in Japy#; and when the animal con- 
tracts itself, the dorsal shields are closely approximated to each 
other. 
The legs are slender, calculated for running; the tarsus long, 
inarticulate, ending in two long, hooked and sharp-pointed 
claws, of which each carries on the outside a long, thin, curved 
appendage. ‘This appendage looks like a seta, but is not placed 
in any depression ; the concavity of its curvature is opposite to 
that of the claw, so that the points approach ; and its apex is a 
little flattened. 
The first abdomen-ring (segmentum mediale), when viewed 
from beneath, exhibits on each side a peculiar appendage, like a 
pocket, taking rise from the pleure, and furnished near its apex 
with two close rows of sete. A row of stiff short sete is also 
observed along the whole posterior margin of the ventral shield. 
The following six rings have no such appendage; but in the 
posterior corners of their ventral shields a conical or subulate 
appendage articulating with the body is observed, and inside 
this, on each side, a little sac, which is capable of being retracted 
inside the edge of the ventral shield, and thus hidden from 
observation. ‘These sacs, which for this reason have hitherto 
escaped notice, consist of a thin membrane; and when pushed 
out, they present at their apex a glandular mass, and a retracting 
muscle is seen, which is fixed to their inside. They correspond 
probably to the sacs discovered by Guérin in Machilis, and in- 
terpreted by him as branchial sacs, analogous to those of the 
Crustacea, for which reason, amongst others, he would incorpo- 
rate Machils with Crustacea (Amn. d. Sc. Nat. 1836, sér. 2. 
tome vy. p. 374, and Compt. Rend. 1836, tom. 11. p. 595). Sepa- 
rate pleural plates are not observable on any of these abdomen- 
rings; but the dorsal shields cover, as in Forficula, the whole of 
