38 



BRITISH OOPEPODA. 



" This species differs considerably from M. viridis. 

 In the first place the cephalothorax is rather broadest 

 behind instead of in the middle, and the three posterior 

 segments are somewhat moniliform, so that their sides 

 do not form an even line. The abdomen is 4-jointed, 

 and the basal segment bears on each side a large 

 plumose hair, which passes backward and outward. 

 Upon the fourth caudal seta (counting from the out- 

 side) is another, rather smaller than the other five. 

 It is so close to the fourth seta that it might easily be 

 overlooked. For the sake of clearness, however, I 

 have in my figure separated them. Length of cephalo- 

 thorax -037 of an inch, of abdomen -012, total '049 ; 

 of antenna '027. Caught at Weymouth, October, 

 1857." 



