THE EXDOPHRAGMAL SYSTEM. 159 



The endopleurites (en, pi.) are also vertical plates, but 

 they are relatively shorter, and their inner angles give off 

 two nearly horizontal processes, one of which passes 

 obliquely forwards (fig. 39, B, h, fig. 42, h.p.) and unites 

 with the paraphragm of the endosternite of the somite 

 in front, while the other, passing obliquely backwards 

 (fig. 39, /i'), becomes similarly connected with the endo- 

 sternite of the somite behind. 



en.pl. 



FIG. 42. AstacvsfnriatHls.PL segment of the endophragmal system 

 ( x 3). aph. arthrophragm ; arth, arthrodial or articular cavity ; 

 cxp, coxopodite of the ambulatory leg ; enpl, endopleurite ; enx, 

 endosternite ; epm, epimeron ; hp, horizontal process of endo- 

 pleurite ; -nipTi, mesophragm ; pph, paraphragm ; #. sternum of 

 somite ; gc, sternal canal. 



The endopleurites of the last thoracic somite are rudi- 

 mentary, and its endost'ernites are small. On the other 

 hand, the mesophragmal processes of the endosternites of 

 the two posterior somites of the head (fig. 39, B, c.ap), by 

 which the endophragmal system terminates in front, are 

 particularly strong and closely united together. They 

 thus, with their endopleurites, form a solid partition be- 

 tween the stomach, which lies upon them, and the mass of 



