4 BRITISH OOPEPODA. 



joints (one to three), and sometimes (Nannopus, Platy- 

 chelipus) is reduced to a small papilla bearing a few setse. 

 The genera in which two non-coalescent ovisacs occur 

 are very few, probably only two Diosaccus and Dela- 

 valia. 



Sub-family 1. LONGIPEDIIN^!, BoecJc. 



The characters which distinguish the genera belong- 

 ing to this section are as follows : The accessory 

 branch of the posterior antenna is largely developed ; 

 mandible-palp 2-branched, the branches springing 

 from a large basal plate ; the posterior foot-jaws are 

 not formed for prehension, having no clawed hand ; 

 the first pair of feet is like the following pairs, both 

 branches being adapted for swimming and not at all 

 for grasping. 



