OTTBODUCTIOIT. 



Vll 



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 branchiostegites 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 



"Sid. I. — Appendages of Penwus canaliculatus. 

 a, Mandibles ; h, first maxilla ; o, second maxilla ; d, first maxillipede ; 

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

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



to which the Prawn belongs by a transverse groove en the 

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

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



