Carpenter — The Aptenjgota of the Seijchelles. 13 



('04, PI. II, f. 26). There is a rounded condyle at the base, and the inner 

 hind edge projects around the hollow into which the iihres of the adductor 

 muscles pass (fig. 75). On the outer edge of the mandible are a number of 

 bristles, most of them bifid like those of the head, but a few simple ; there are 

 also some bifid bristles along the front inner edge, near the molar area, which 

 is beset with a number of short, strong spines (fig. 76). Beyond these is a 

 blunt projection, and the apex has three prominent but not very sharp teeth ; 

 a slight difference between the apices of the right and left mandibles is 

 noticeable. The mandible is worked by at least six distinct muscles. There 

 are two retractors (fig. 75 re), inserted into the inner median ridge — 

 one by a single tendon, and the other by a number of slender tendons. A 

 posterior adductor muscle (fig. 75 ad. p.), with a tendinous insertion, pulls at 

 the basal region of the mandible, while three median adductors (fig. 75 «(£), 

 one large and two smaller, with fibres radiating so as to be inserted along the 

 inside of the outer wall, serve to draw the mandible strongly towards its 

 fellow. A closely similar arrangement in Lcpisma saccharina has been 

 described and figured by Bonier ('09, pp. 104-5, fig. 2). 



The tongue in Isolepisnia (fig. 77 hy) is small, with the tip hairy, and the 

 peduncles almost parallel. The viaxillulae (fig. 77 onx/) have a roughened 

 apex, with fine, short bristles. No differentiation into galea and lacinia — so 

 apparent in a Machilid maxillula — is here distinguishable. Hansen twenty 

 years ago pointed out that the maxillulae of the Lepismidae are feebly 

 developed as compared with those of the other Thysanura, recalling the con- 

 dition found in earwigs ('93), but no entomologist has hitherto given attention 

 to these interesting structures in this family. 



The maxilla (fig. 78) resembles in its main features that of a Lepisma 

 figured by Escherich ('04 ; PI. II, fig. 29). The tip of the lacinia has two 

 strong teeth ; its inner edge is drawn out into seven delicate teeth, forming a 

 " comb " (fig. 78 1), proximal to which are eight prominent bristles. The 

 musculature of the maxilla is like that found in biting insects generally ; there 

 is a strong protractor muscle (pr.) on the inner edge of the cardo (c), while 

 the muscles for working the galea and lacinia (g. m. and /. m.) originate at the 

 proximal end of the stipes, and have their fibres converging to the insertions 

 at the bases of the lobes. 



The labium (fig. 79) has a short and broadly arched sub-mentuni (s. m.), 

 the raentum (m), galeae {g), and laciniae {I) being small, somewhat rugose and 

 spiny ; the distal edge of the lacinia is drawn out into a delicate ridge. The 

 four-segmented labial palp has a very broad and blunt terminal segment 

 (fig. 79^.). 



In both sexes the inner process of the ninth abdominal sub-coxa (figs. 80, 



