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Male — length 2,4 mm. 
The male resembles the female in general appearance, but the abdomen is composed 
of five segments. The second segment has no spiniform process on the right side. 
The middle joints of 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 first 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-thirds 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, nine females and four males. 
This species is dedicated to the memory of my friend the late J]. ©. 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 herdmani nov. sp. Plate XLIX, figs. g—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 thompsont. 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 LIOX, 
figs. 9 and 10). 
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