i8o 



The antennules are eighteen-jointed and extend to the end of the genital segment. The 

 third joint is very small (Plate XLIX, fig. 12). 



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

 are almost similar to those of Calanopia elliptica. The apical portion of the second pair of 

 maxillipedes is composed of five joints. 



The fifth pair is symmetrical. The first joint of the exopodite is comparatively long and 

 slender. The distal portion of the outer margin is furnished with two moderately stout spines. 

 The second joint is narrow and spiniform. It terminates in a moderately long and slender spine. 

 The outer margin of the joint is furnished with two small spines. There is no inner edge spine 

 as in Calatiopia thompsoni (Plate XLIX, fig. 1 3). 



Male — length 1,7 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 slightly inflated. The upper margin of the 

 proximal and distal hinge joints is fringed with fine spines. 



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 slender and rather cylindrical. The second joint 

 is equal to two-fifths of the length of the first joint. The apex terminates in two moderately 

 long spines. The outer one is distinctly longer and stouter than the inner one. The outer 

 margin is furnished with one slender spine. The first joint of the right exopodite is nearly oval 

 in outline, and the palm is simple. The claw-like second joint is spoon-shaped, but it has no 

 basal tooth (Plate XLIX, fig. 16). 



This species has a general resemblance to Calanopia elliptica, but the two sexes can 

 readily be separated by the difference in the proportional length of the abdominal segments, by 

 the absence of a tooth on the right side of the second segment of the male abdomen, and by 

 the structure of the fifth pairs of feet. 



Occurrence. — One female and five males were obtained from the plankton collected 

 at the following stations. 



Stat. 109, one male. — Stat. \\J'\ one male. — Stat. 141 (Hensen vertical net, 1500 metres 

 to surface), one male. - - Stat. 142, one female and one male. — Stat. 143 (HENSEN ver- 

 tical net, 1000 metres to surface), one male. 



This species is named in compliment to Professor W. A. Herdman, F. R.S., whose 

 enthusiasm and example have done so much to encourage the systematic investigation of the 

 fauna of the Irish Sea, that has been carried on during the last twenty years by the Liverpool 

 Marine Biology Committee. His Oceanic Researches have also been extensive. The reports on 

 the 'Challenger' Ascidians and the Investigation of the Ceylon Pearl Oyster Beds are well 

 known works. The late I. C. Thompson and the present writer have had many facilities to 

 study Oceanic Copepoda by the examination of collections of plankton obtained by him at 

 various times. 



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