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Male — length 2,4 mm. 



The male resembles the female in general appearance, but the abdomen is composed 

 of live segments. The second segment has 110 spiniform process on the right side. 



The middle joints ot the right antennule are considerably inflated. The upper margin 

 of the proximal and distal hinge joints is fringed with fine spines (Plate XLIX, fig. 7). 



The antennae, mandibles, maxillae, maxillipedes and lïrst four pairs of swimming feet 

 are similar to those of the female. 



The exopodite of the left fifth foot is moderately broad. The second joint is short. It 

 is equal to two-thïrds of the length of the first joint. The apex is furnished with two spines, 

 and a broad, flat, finely denticulated process. The distal end of the posterior surface of the 

 joint bears a curved spine, like a small chela. This spine is almost invisible when the preparation 

 is reversed and the anterior surface placed uppermost. The claw-like joint of the right exopodite 

 is spoon-shaped. It is furnished with one small basal tooth (Plate XLIX, fig. 8). 



This species is easily separated from any of the other members of the genus, by the 

 presence of distinct side hooks on the cephalic segment of both sexes. It is a true Calanopia 

 and is larger than any of the other species. 



Occurrence. — Seventy-two females and eighty-eight males were obtained from the 

 plankton collected at the following stations. 



Stat. 16, twenty-two females and ten males. — Stat. 142, twenty-nine females and sixty-nine 

 males. — Stat. 205, twelve females and five males. — Stat. 213, mne females and four males. 



This species is dedicated to the memory of my friend the late I. C. Thompson of 

 Liverpool, a well known worker amongst the Copepoda. He was the first to seriously investigate 

 the pelagic and littoral forms of the Irish Sea. He also did a considerable amount of valuable 

 research in the plankton of the great oceans. 



4. Calanopia herdinani nov. sp. Plate XLIX, figs. 9 — 16. 



Female — length 1,8. 



Viewed from above, the body appears elongate ovate, and moderately robust. The 

 forehead is narrowly rounded. The cephalic segment is without side hooks. The last thoracic 

 segment is produced posteriorly into spiniform processes. The rami of the rostrum are rather 

 stout. The distal end of the inner margin of each ramus is slightly barbed. The excavation is 

 wedge-shaped (Plate XLIX, fig. 11). 



The abdomen is composed of two segments. The combined length of the abdomen and 

 furca is contained nearly two and one-third times in the total length of the cephalothorax, from 

 the frontal margin to the base of the genital segment. The genital segment appears short and 

 tumid in dorsal view. The ventral surface is furnished with a small spine near the anterior end, 

 but it is not produced into a knob at the distal end as in Calanopia thompsoni. The genital 

 segment is very slightly longer than the second segment. The second segment is about twice 

 as long as broad. The furcal joints are two and a half times longer than broad (Plate XLIX, 

 figs. 9 and 10). 



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