THE CRUSTACEA 



The classification of the Branchiopoda commonly adopted differs 

 from that given below in grouping together the Anostraca, 

 Notostraca, and Conchostraca as a single order, Phyllopoda 

 (Latreille, 1802), 1 distinguished from the Cladocera chiefly by the 

 greater number of somites and appendages and by the prevalence 

 of metamorphosis in development. The groups of the Phyllopoda, 



FIG. 32. 



Polyartemia forcipatu, one of the Anostraca. x 5. (After Sars.) A, female, dorsal view ; 

 B, male, lateral view, a', antennules ; a", antennae, very small in the female but greatly 

 enlarged and three-branched in the male; f.a, "frontal appendage"; p, paired penes of the 

 male. There are nineteen limb-bearing trunk-somites, followed, in the male, by six limbless 

 somites (besides the telson), of which the first and second are partly coalesced to form the 

 genital segment. In the female the limbless region of the trunk is unsegmented. 



however, differ among themselves in characters which are at 

 least as important as those separating the Cladocera from the 

 Conchostraca, and it seems desirable to recognise this by giving 

 them the rank of orders. 



1 Unfortunately some writers, following Glaus, have transposed the names 



Branchiopoda and Phyllopoda, applying the latter to the sub-class and the former 



to one of its divisions, but this use is not sanctioned either by priority or by 

 universal custom. 



