10 k Canadian Arctic Expedition, 1913-18 



the Arctic ocean, and the adult male is only 1-45 mm. long. Aside from the 

 presence or absence of a rostrum, the Canadian Arctic forms agree with Gaidius 

 tenuispinus in having the inner branch (Ri) of the second legs (p.2) two-jointed 

 and in lacking an outer seta (se) on the first joint of the outer branch (Re 1) of 

 the first legs (p. 1). Sars observed that G. tenuispinus sometimes occurs in the 

 same gatherings with Ch. obtusifrons, both species ranging through the Polar 

 basin crossed by Nansen. 



The inner ramus of the mandibular palp is not so "unusually small" as is 

 required by the definition of Chiridius; the teeth of the mandible have simple 

 points. The anterior antennae are 24-jointed, joints 8 and 9 being coalescent, 

 the terminal joint distinct and short; the entire appendage is not longer than 

 the forebody. The second basal joint (B2) of the second maxilliped (mp2) is 

 hardly longer than the Bl; the first inner seta (si) of B2 is inserted distad of the 

 middle of the joint, the portions of the joint proximal and distal to the insertion 

 of this seta being as 2: 1. 



6. Euchaeta norvegica Boeck, 1872. 



I noted only a single damaged immature female, with three-jointed abdomen, 

 in the gathering from station 29^4, depth 150 fathoms; a vertical haul with net 

 number 5 from to 50 fathoms in an open water lane in pack-ice, 70° 20' N., 

 140° 30' W. There was a very small quantity of plankton for such a great 

 column of water. In the same vial with the Euchaeta there was one Metridia 

 longa 9, and half a dozen Oithona similis. 



Euchaeta norvegica is a characteristic North Atlantic and Arctic species. 

 It occurred at numerous stations in Dr. Hjort's Canadian Fisheries Expedition 

 1914-15,' but not in Professor Herdman's traverses of the Atlantic to which 

 reference will be made later. At Passamaquoddy Bay it forms part of the food 

 of the Pollack. 



7. Centropages mcmurrichi, n. sp. 



This species occurred at several stations already mentioned: Tables I, 



11 and IX. It was first obtained off the British Columbian coast by Professor 

 J. Plaj^fair McMurrich^ in a patch of "brown water" off the entrance to Esperanza 

 inlet , on the west coast of Vancouver island on September'll, 1912. He identi- 

 fied it as Centropages hamatus (Lilljeborg 1853), whilst noting differences in the 

 armature of the genital segment of the female and in the structure of the fifth 

 legs. It has the ventral recurved hook of C. hamatus 9 in front of the genital 

 pore but the remaining setulose armature of the genital segment is distinctive. 

 The other principal specific character is afforded by the strong unguiform process 

 on the inner side of the second joint of the outer ramus of the fifth foot (p5 Re2 9 ). 

 In C. hamatus this process is smooth and less than half the length of the third 

 joint (p5 ReS). In the present species the process is at least two-thirds the 

 length of ReS and is denticulated along its outer edge. The relative dimensions 

 of anal segment and caudal furca in the female are: anal segment 6, f ureal 

 length 11, width of f ureal ramus 3. 



In addition to the stations named above, a single female, accompanied by 

 numbers of Paralabidocera, was taken at station 21 d,e,f, with net number 3, 68° 

 41' N., 165° 10' W., temperature 45-5° F., surface, August 16, 1913. A female 

 from station 20a, July 30, 1916 (Table IX) carried a spermatophore. 



The spinules on the genital segment of the female include a pair of antero- 

 ventral groups arranged in a comb-like row right and left of the swollen base 



1 A. Willey: Report on the Copepoda obtained in the Gulf of St. Lawrence and adjacent waters 1915. 

 Canad. Fish. Exped. 1914-191,'). Department of the Naval Service Bluebook, pp. 173-220, Ottawa 1919. 



' ,J. P. McMurrich: Notes on the Plankton of the British Columbia Coast. Trans. Roy. Soc. Canada 

 (ser. Ill), vol. X, September, 1916, p. 77-8, f. 1-3. 



