INTEODUCTION. 



vn 



pointed process the rostrum ; its middle portion corresponds 

 to the terga of the segments or somites which it covers ; the side 

 portions which constitute a pair of broad flaps covering the gills 

 and corresponding to the pleura of the cephalothoracic segments, 

 are called the brancliiostegites or gill-covers. The appendages 

 belonging to the cepthalothorax may be conveniently regarded 

 as falling into two groups the appendages of the head or 

 cephalon, and the appendages of the thorax. The division 

 between the two is indicated by a fold the cervical fold at the 

 side of the mouth, and is marked out also in most of the group 



Fig. I. Appendages of Penceus canaliculatus. 



a, Mandibles ; b, first maxilla ; c, second maxilla ; d, first maxillipede ; 

 e, second maxillipede ; f, third maxillipede ; g, leg of first pair; ex, 

 exopodite ; ep, epipodite ; 1-7, joints of the endopodite. 



to which the Prawn belongs by a transverse groove on the 

 carapace, the cervical groove, which, however, is but slightly 

 indicated in the Prawn. The thorax, as thus marked off, consists 



