120 



Remarks. This form was briefly mentioned by Boeck in the above- 

 mentioned paper, and some figures of it were given by the present author in his 

 account of the Crustacea procured during Nansen's Polar Expedition. It is nearly 

 allied to the 2 Mediterranean species, H. spinifrons and H. papillatus, recorded 

 by Glaus; but it is of larger size than either of them, and moreover differs in 

 the relative length of the anterior antenna?, and in the structure of the last pair 

 of legs in the male. 



Occurrence. Boeck first found this form at Haugesund, west coast of 

 Norway. I have myself taken it in several places, from the Christiania Fjord 

 and as far north as the Lofoten Islands, but only in greater depths, of more than 

 150 fathoms. It also occurred not unfreqnently in some plankton-samples taken 

 from deep water in the open sea during the cruise of the "Michael Sars" in 1900. 



Distribution. Polar basin crossed by Nansen, in several places rather 

 abundantly (the present author), Greenland, Faroe Channel (Norman's collection). 



Glen. 21. HalOptllUS, Giesbrecht, 1898. 



Syn: Hemicalanus, Claus (not Dana). 



Generic Characters. Body subdepressed and highly pellucid. Cephalo- 

 some comparatively large; more or less produced in front, and without any 

 distinct cervical depression; rostral filaments slender and recurved. Lateral parts 

 of last segment of metasome not expanded. Urosome comparatively short, com- 

 posed in female of 4, in male of 5 segments. Caudal rami perfectly symmetrical, 

 not much produced, and somewhat divergent, setae normally developed, and richly 

 plumous. Eye wholly absent. Anterior antennae very slender and narrow, with 

 some of the bristles much elongated; left antenna in male geniculate. Posterior 

 antennae with the inner ramus greatly produced, outer ramus comparatively small. 

 Mandibles with the masticatory part very narrow and bifurcate at the tip, palp 

 slender, with the inner ramus much longer than the outer. Maxillae with the 

 inner ramus of the palp small, but distinct, outer ramus considerably produced, 

 and carrying at the tip long plumous setae. Anterior maxillipeds of moderate 

 s'ze, with all the lobes distinctly developed, distal setae not claw-like. Posterior 

 maxillipeds much larger than the anterior, terminal part 5-articulate and clothed 

 with long, anteriorly-curving setae. Legs not very powerful, outer ramus of 2nd 

 to 4th pairs of moderate size, with the terminal joint far less expanded than in 



