102 THE CRUSTACEA 



which in the Eucopepoda, as in other Crustacea, opens on the 

 maxilla, but in the Branchiura on the first thoracic appendage. It 

 seems more probable, however, that a shifting of the aperture has 

 taken place than that the appendages do not correspond serially 

 in the two groups. 



SUB-CLASS COPEPODA, H. Milne-Edwards (1830). 

 ORDER 1. Eucopepoda, Glaus (1875). 



Paired compound eyes absent ; genital apertures on the seventh 

 trunk - somite ; thoracic limbs without flagellum ; fertilisation by 

 spermatopli ores. 



SUB-ORDER 1. Gymnoplea, Giesbrecht, 



Last thoracic somite firmly connected with the preceding somite and 

 movably articulated with the first abdominal somite ; last pair of thoracic 

 appendages in female similar to preceding pair, or reduced or absent, in 

 male always present and modified as copulatory organs ; one or neither 

 of the antennules geniculate in male ; eggs deposited singly or carried in 

 a single packet ; heart generally present ; vas deferens unpaired, its 

 opening unsymmetrically placed. Free-living forms, mostly pelagic. 



TRIBE 1. AMPHASKANDRIA, Giesbrecht. 



Antennules of male not geniculate, with more numerous aesthetascs 

 than in female. 



Family CALANIDAE. This extensive group is divided by Sars into 

 twelve families. Most of these correspond to sub-families recognised by 

 Giesbrecht. Calanus, Leach (Fig. 41) ; Eucalanus, Dana ; Rhincalanus, 

 Dana ; Calocalanus, Giesbrecht (Fig. 42) ; Paracalanus, Boeck ; Pseudo- 

 calanus, Boeck ; Aetideus, Brady ; Euchaeta, Philippi ; Phaenna, Glaus ; 

 Scolecithrix, Brady ; Diaixis, G. 0. Sars ; Stephos, Scott ; TharyUs, G. O. 

 Sars ; Pseudocyclopia, Scott. (The families represented by the last eight 

 genera are separated from the Amphaskandria by Sars to form a division 

 Isokerandria.) 



TRIBE 2. HETERARTHRANDRIA, Giesbrecht. 



One of the antennules geniculate in male. 



Family GENTROPAGIDAE. Divided into eight families by Sars : 

 Centropages, Kroyer ; Diaptomus, Westwood ; Pseudodiaptomus, Herrick ; 

 Heterocope, G. 0. Sars ; Lucicutia, Giesbrecht ; Temora, Baird ; Metridia, 

 Boeck ; Heterorhabdus, Giesbrecht ; Pleuromamma, Giesbrecht ; Arietellus, 

 Giesbrecht. Family PSEUDOCYCLOPIDAE. Pseudocyclops, Brady. Family 

 CANDACIIDAE. Candacia, Dana. Family PONTELLIDAE. Divided into 

 four families by Sars : Pontella, Dana; Parapontella, Brady; Acartia, 

 Dana ; Anomalocera, Templeton ; Tortunus, Giesbrecht. 



