a Famili/ of Thy samwa. 375 



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 AVestwood 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 antennae. 



The prothorax is considerably smaller than either the meso- 

 tliorax or metathorax, which latter are of about equal size. 

 The transverse folds which separate the dorsal shields are not 

 chiitinized in Cumpodea as in Japyx; and when the animal con- 

 tracts itself, the dorsal shields are closely approximated to each 

 other. 



The legs ai'e 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 pleurse, and furnished near its apex 

 with two close rows of setse. A row of stiff short setse 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 venti-al 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 Guerin 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 Machilis with Crustacea (Ann. d. Sc. Nat. 1836, ser. 2. 

 tome v. p. 374, and Compt. Rend. 1836, tom. ii. 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 



