8 



Instead of taking an even sweep downwards the carapace 

 passes outwards almost horizontally and then suddenly 

 bends inwards and passes down to the bases of the walking 

 legs. An examination of a rough section of the animal 

 will show that at the base of the legs the carapace turns 

 suddenly upwards and is continuous with the membranous 

 wall of the spacious Branchial Chamber (PI. IV, fig. 56, 

 br. ch.). The space between the ventral part of the 

 carapace and the base of the legs is so very small, and 

 moreover is so well guarded by long setae that no water 

 can enter the branchial chamber at this border, as is the 

 case in the Macrura. There are, however, two openings 

 into the branchial chamber — the small posterior inhalent 

 branchial aperture, above the coxopodite of the last 

 pereiopod, and the larger anterior inhalent branchial 

 aperture, situated immediately in front of the coxopodite 

 of the chela. The ventral part of the carapace turns 

 forward in front of the latter opening, and passing around 

 the mouth it fuses with the pre-oral cephalic sterna. The 

 portion of the carapace which passes around the mouth is 

 turned inwards at each side to form a chamber which lies 

 immediately in front of the Branchial Chamber. This 

 may be called the Pre branchial Chamber. Its roof is 

 membranous and is fused on its inner side with the 

 epistoma and with the endopleurites of the two post-oral 

 cephalic somites, and probably represents the epimera of 

 the third, fourth and fifth cephalic somites. The Pre- 

 branchial Chamber will be described in detail in the 

 seel ion on Respiration. 



Both the dorsal and the inflected portions of the 

 lateral region of the carapace were designated the 

 " branchiostegite " by Milne-Edwards because they 

 enclose the branchial cavity. 



Anteriorly the dorsal surface of the carapace is 



