ANATOMY. 63 



generally run to or near to the inner sides of tlie coxae 

 of the first legs. The sternum is sometimes not a mere 

 blade, but is spread out on the side where it is most 

 deeply embedded in the body, and forms a bayonet- 

 shaped sclerite, one edge of which comes to the ventral 

 surface (PL C, fig. 6). In some cases the central shaft 

 of the sternum may be very short, or even entirely 

 absent, only the arms remaining ; or the arms may be 

 absent, leaving the shaft only. In rare cases the 

 sternum is continued sufficiently far back to be joined 

 to a chitinous ring surrounding the genital aperture ; 

 in the female of Glycyph'agw dispar, where there is not 

 any shaft to the sternum, the ends of the two arms are 

 joined to such a ring. 



The epimera are blades which are frequently more 

 or less expanded at the end nearest to the median line 

 of the body ; that end is usually rounded, while the 

 outer end, next the coxge, is more commonly thickened, 

 but not so much expanded. The edge which reaches 

 the ventral surface is often also somewhat thickened, 

 being thus stronger than the edge within the body. 

 The epimera are seldom straight, they are mostly 

 curved, and sometimes have a complicated shape ; they 

 also generally have the blade slightly turned or twisted 

 within the body, giving a certain resemblance to one 

 blade of a steamer's screw in shape. This turning 

 within the body in semi-transparent species causes the 

 epimeron, when seen from the ventral surface, to look 

 spatulate. This appearance is generally much more 

 noticeable in the epimera of the two anterior pairs of 

 legs than in those of the two posterior pairs ; indeed, 

 the former are usually the largest and best developed 

 in most respects (see PL XIX, figs. 4, 7, 12). The first 

 or second epimera may be joined to the sternum, or 

 may be free at their inner ends ; they may be joined to 

 a ring surrounding the genital aperture, as in the 

 female of Grlycyphacjus dispar, or may be joined by cross 

 pieces at their inner ends or otherwise, as in the male 

 of Lentunyula alyivorans (PL I, fig. 3). 



