of the North Atlantic and of North- Western Europe. 705 



Peduncle of the principal branch of the antenna twice and a-half as long as the 

 short-jointed apical portion, which has plumose swimming setse, setse more 

 than half as long again as the limb itself, the princijDal seta of the secondary 

 branch is more than twice as long as the sensory filaments. Caudal laminge 

 bearing seven pairs of curved spines. Length, 2*2 mm. ; height, 1"8 mm. ; width, 

 1'6 mm. 



Atlantic Ocean; taken at the surface, and in various depths (Claus) ; Gibraltar 

 (Chierchia, /Je G. W. Miiller). 



A single specimen was noticed amongst the "Challenger" captures, but the 

 exact locality is doubtful. The male of this species has not yet been seen. 



Our description is taken in part from that given by Dr. Claus ; the one 

 specimen which we have had the opportunity of examining being imperfect. 



Section III. — Cladocopa, G. O. Sars, 1865. 



Fam.— POLYCOPID-ffi, G. 0. Sars. 



Shell round, or nearly so, valves thin, sub-equal, without the antennal sinus 

 usually found in Myodocopa. Antennules and antennae adapted for swimming, 

 both with large muscular basal joints, and long terminal setae ; the former not 

 branched nor geniculated ; the latter biramose, both branches natatory. Man- 

 dibles distinctly toothed, furnished with a palp, which is not pediform, ending in 

 setas, not in ungues. Only two pair of limbs behind the mandible, and these 

 formed for swimming, the first with one very minute seta-bearing lobe on the 

 basal joint, and a long laminar appendage attached to the antejDenultimate joint; 

 the second of these limbs is much smaller then the first, its three-jointed basal 

 joint wide and expanded on one side into a seta-edged branchial plate. Caudal 

 laminse broad and rather short, their hinder margin bearing a series of ungues. 

 No eyes. No heart. Intestine forming a simple sac. 



Genus Polycope, G-. 0. Sars, 1868. 



Shell nearly round, texture thin and fragile, corneous, and only slightly 

 calcareous. No frontal tentacle, but in its place two short ciliated setae. 

 Antennules (PI. lxvii., fig. 1) three- jointed, terminating in very long setse. 

 Antennae (PI. lxvii., fig. 2) with the branches sub-equal in length, the larger 

 branch similar in structure to the natatory branch in Cypridinidae, nine-jointed, 

 and bearing lateral and terminal swimming setae, the other branch three- jointed 

 ending in a bunch of setae. Mandible (PL lv., fig. 13) with a masticating toothed 

 lobe, palp two-jointed, the first joint strong, and furnished above with a small 



