n Family 0/ Thysaaura. 369 



tioned ; and this I look upon as representing the cardo or hinge 

 of the maxilla. The outer lobe (fig. 2 e) is membranaceous, and 

 has near its anterior margin a small conical protuberance. 

 There is a distinct palpiger (fig. 2 g) carrying a biarticulate 

 palpus (fig. 2/). The lingua (fig. 2 h) is in this genus propor- 

 tionally very small, linguiform, and armed with short setae. The 

 paraglossse (fig. 2 i i), on the contrary, are very large and bi- 

 lobate. Of the muscles moving all these parts some are fixed 

 to the inner surface of the skull, others to the oft-mentioned 

 framework, which, in its turn, with all that is connected with 

 it, can be pushed forward and drawn back by special sets of 

 muscles, as shown in figure 2. 



The labium reminds one somewhat of the same organ in Ulo- 

 nata, and consists of a deeply bifid plate covering the mouth 

 from beneath. Its most striking featui-e is the existence of two 

 large retractile warts, clear as water, which I suppose to corre- 

 spond to the inflations discovered by Latreille on the labium of 

 Machilis (Nouv. Ann. du Museum, 1832, i. p. 171). But for this 

 analogy, one might be tempted to look upon them as a kind of 

 palparia which these blind animals might well need, but which 

 are wanting in both pairs of palpi. I regret that my scanty 

 material did not permit a proper examination of their histological 

 structure. On each side of the fissure in the middle of the 

 labium two component pieces (centres of chitinization) may be 

 distinguished, one behind the other, which perhaps correspond 

 to the lobes observable on the third pair of appendages of the 

 mouth in Ulonata. Further behind, a third pair of plates is 

 observed, one on each side, which perhaps represent the stipites 

 of the third pair of mouth-appendages ; and in an emargination 

 on each of these plates, the short, conical, sparsely haired, and 

 strongly chitinized palpus is inserted. 



There is no mentum. The hypostoma forms a rather large 

 obversely cordate plate, placed near the posterior border of the 

 underside of the head, between the inflected margins of the 

 occiput. 



The antennae consist of many short joints furnished with 

 verticillate setae; the individual joints ax'e inversely conical or 

 almost spindle-shaped, so that the general outline of the antennae 

 becomes filiform or slightly moniliform. The last joint is 

 smaller than the others and slightly conical. The antennae are 

 placed on a protuberance which is separated from the skull by 

 a fine suture, but does not constitute a basal joint, as it is im- 

 moveable, the muscles of the antennae inserting themselves only 

 on the base of the following moveable division. 



There is no vestige of eyes. 



The skull is supported by a thin chitinous piece, which is 

 Ann. ^ Mag. N. Hist. Ser. 3. Vol. xx. 25 



