a Famihj o/Thysanura. 367 



diirae never belong to the last ring, but take their rise from the 

 ventral shield of one of the preceding rings, both when they 

 preserve their original plain form and when they are transformed 

 into a springing-apparatus. 



Neither in Jopyx nor in any species of Campodea have I been 

 able to discover eyes, though both Guerin and Nicolet assert 

 that they have found eyes in the species of Campodea examined 

 by them. 



Japyx, Hal. 



Cerci breves, inarticulati, cornei, forcipis instar. 



Segmentum ultimum maximum, psenultimum breve, scuto 

 ventrali fisso. 



Mandibulse paululum compressae, serratse. 



Mala interior maxillge lobis quinque laciniatis instructa. 



Palpi maxillares biarticulati. 



Labium verrucis (palpariis ?) duabus anticis permagnis iii- 

 structum. 



Palpi labiales conici, setis simplicibus muniti. 



Antennae setaceae, articulo ultimo parvo, minore quam pjen- 

 ultimo, conico. 



Oculi nulli. 



Unguiculi simplices, insequales, onychio unguliformi. 



Spiracula dena. 



The following description of the mouth in this genus applies 

 in all essential respects to the whole order of Thysanura gene- 

 rally :— 



The mandibles (fig. 1 a) are elongated, flat, and their basal part 

 attenuated into a point without any vestige of condyles. The 

 proi)ortion of their breadth to their length is as 1 to 6 or 7, 

 and they are therefore comparatively much more robust than 

 those of Antliata and Rhynchota, which are setiform or subuli- 

 form. But the principal peculiarity of the mandibles in Japyx 

 and other Thysanura is that they are hollow^, and that their great 

 flexors (c) penetrate into their interior through a longitudinal slit 

 or fissure along their inward edge, and fix themselves inside the 

 mandible on the wall of the cavity opposite the fissure ; whilst 

 in other insects the mandibles are solid, and the muscles are all 

 fixed to their outside by tendons. The opposite ends of the 

 flexors of the mandibles, as well as of their tensors, in Japyx 

 are attached to a chitinous plate (fig. 1 h) situated between the 

 mandibles, and steadied by a double set of muscles (fig. 1 g h). 

 Thus the mandibles can be approached to one another; but, in 

 order to give this movement sufficient precision and strength, 

 the mandibles must turn round some firm centre of movement ; 

 and as they do not articulate with the skull as free biting 



