18 



b. The 3rd pair of legs hare nn opipodito and a podo- 

 branch, tlie 4th pair have nn upipodito : 

 a. Exopodites of the 2nd maxilliped* much 

 longer than the endopodites : plenro- 

 branchite Binall and slender hut 

 plumose ... PLISIOPHICH. 



fi. Exopudites of the 2nd innxillipedH very 

 much shorter thai! the endopodites : 

 pleurobrancluK) large ... ... AKISTAOPSIS. 



ii. An hepatic spine : 



a. The 3rd pair of legs havo an epipodite, but no 



podobranch, the 4th pair have no epipodite ... HCPOMADCS. 

 6. The 3rd pair of legs have an epipodite and a podo- 

 branch, the 4th pair have au eplpoditu : rostrum 

 many-toothed dorsally ... ... ... ARISTAOMORPIU. 



2. Both the antennular flngellaare long: the first joint of the mandi- 

 Imliir palp is distinctly foliaceons (and is much longer and 

 broader than the 2nd joint) : 



i. The endopodites of the 2nd maxillipeds are of the usual 



subpediform shape ... ... ... BBNTHISICTMUS. 



ii. The merus of the 2nd maxillpeds is a thin oval leaf com- 

 pletely concealing the next 3 joints when they are 

 flexed ... ... ... ... ... GENNADAS. 



Subfamily Peneince. 

 PENEDS, Fabr. 



Ptnaeus Fabricias Ent. Syst. Suppl. p. 408 : Milne Edwards, Hist. Nat. Crnst. II. 411 (ub tynen.) : Spenoe 

 Bate, Challenger Crustacea Macrnra, p. 229. 



Carapace with a well developed rostrum, which may be toothed dorsally 

 and ventrally, or dorsally only. Abdomen long, with some of the posterior 

 somites compressed and cai'inated. Eyes large and subglobular. 



The basal joint of the antennule is hollowed dorsally for the reception of 

 the eye, its outer edge is produced anteriorly into a spine, and from the 

 proximal end of its inner edge there springs a conspicuous twisted setose 

 scale. The antennular flagella are cylindrical : they are commonly subequal in 

 length and either short or not very long, but occasionally one of them is much 

 elongated (e. g. subgenus Xiphojiencnx). 



Antennal scale large, the outer edge rigid and anteriorly acute : antennal 

 flagellum long. 



The mandibular palp is large and broadly foliaceous, its 2nd joint is 

 vastly larger than its 1st. The palp of the, 1st maxillae commonly ends in a 

 little, distinctly articulated, flagellum. 



The exopodite of the external maxillipeds is a compressed stiffish joint, 

 as long as, and quite similar to, that of the 2nd maxillipeds. 



