THE ENDOPHRAGMAL SYSTEM. 159 
The endopleurites (en.pl.) 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, h’), becomes similarly connected with the endo- 
sternite of the somite behind. 
Fig. 42.— Astacus flnviatilis,—A segment of the endophragmal system 
(x 8). aph, arthrophragm; arth, arthrodial or articular cavity ; 
cxp, coxopodite of the ambulatory leg ; enpi, endopleurite ; ens, 
endosternite ; em, epimeron; hp, horizontal process of endo- 
pleurite ; mph, mesophragm ; pph, paraphragm ; s, sternum of 
somite ; sc, sternal canal. 
The endopleurites of the last thoracic somite are .udi- 
mentary, and its endosternites 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 
