70 BRITISH COPEPODA. 



appendage. The following formula represents the 

 relative lengths of the various joints : 



1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11. 

 9 7 2 1 2 5 2i 2i 3 ^3 4 



Posterior antennae (fig. 3) 4-jointed, the last joint 

 armed at the apex with two strong lancet-shaped 

 spines, together with one long and four or five very 

 short setae ; at the base of the external margin are 

 also a few small setae ; the second joint gives origin to 

 a 1-jointed secondary branch, which terminates in a 

 long plumose seta. Mandible (fig. 4) simple, consist- 

 ing of a short stout peduncle bearing a very long 

 plumose seta (probably also a filiform palp, though I 

 have not seen this). Maxillae (fig. 5) composed of two 

 stout digits, one of which bears three, the other four, 

 stout, curved, and densely plumose setae. The foot- 

 jaws are precisely similar to those of Artotrogus. 

 Siphon (fig. 6) excessively long and slender, reaching 

 as far as the middle of the caudal segments. Outer 

 and inner branches of the swimming-feet nearly equal 

 in length, 3-jointed, all the joints much constricted at 

 the base (fig. 9), first and second joints dilated at the 

 apex, third elongated and narrow; the distal margins 

 of the first and second joints are strongly dentated, 

 and in the inner branch are, at the outer angles, pro- 

 duced downwards into sharp spines ; the marginal 

 spines of the outer branch are long and dagger- 

 shaped, the last joint of both branches bearing a long 

 subulate and much attenuated apical spine. Fifth 

 pair of feet (fig. 10) stout, 2-jointed, first joint shorter 

 than broad, and bearing one long seta, second longer 



