NO. I 



INSECT TIIORAX-r-SNODCRASS 



23 



important to note that the eupleural and trochantinal sclerites of 

 Eoscntomon fomi a group of small plates arched over the coxal base, 

 and that in this way they correspond with the pleurites in a pterygote 

 pleuron. It may be questioned whether the plates of the eupleural 

 series in Eosentomon are to be identified individually with specific 

 pleural sclerites of winged insects, as Prell suggests, but it is true, 

 at least, that they occur in homologous parts of the pleural area. 

 There can be little doubt, however, that the trochantin is the same 

 sclerite in both insect groups. In Eoscntomon its anterior part tapers 

 downward and ends in a recurved point articulating with the anterior 



Fig. 8. — Mesothorax of a proturan, Eosoitojiwii. gcriiuuiiciDii. (Figure from 

 Prell, 1913, but differently interpreted, and re-lettered.) 



The dorsum contains a tergum (T) with narrow precosta (Pc) separated by 

 antecostal suture (ac), and two posterior weakly chitinized regions (x, y). 

 The pleural area contains a dorsal series of tergo-pleurites (a, b, c, d), a 

 ventral group of true pleurites (e, f, g, h) about the base of the coxa {Cx), 

 and a trochantin (Tn) arched over the coxa. 



ventral rim of the coxal base, while its dorsal part, Prell says, articu- 

 lates both with the dorsal edge of the coxa and with the median 

 pleural plate {g) above it. 



In the Chilopoda, the pleural regions of the leg-bearing segments 

 contain a number of small sclerites. The more dorsal plates in each 

 segment are probably tergopleurites, but those immediately above and 

 before the base of the leg would appear to represent the eupleural and 

 trochantinal sclerites of the Protura. In Lithohiiis forficatus, as 

 figured by Verhoeff (1903), there are two sclerites lying dorsal to 

 the base of the coxa (fig. 9), of which Verhoeff calls the upper one 

 (o) the " anppleure," and the lower (Tn) the " katopleure." A third 

 (p), lying before the coxa, Yerhoefif regards as the "trochantin"; 



