18 



ramus a little shorter than the inner, and 7-articulate. 2nd joint of inner raraus 

 in the 2nd and 3i'd pairs of legs with an obliquely transverse row of spinules on 

 the hind face. Last pair of legs with the distal joint narrow linear, carrying on 

 the tip a slender spine, outside which a much smaller spinule is secured. 



Male differing considerably in its external appearance from the female. 

 Cephalosome somewhat incrassated and exhibiting along the dorsal face an obtuse 

 keel, front considerably more prominent than in female. Urosome rather slender, 

 5-articulate, with the 2nd segment the largest; caudal rami, as in the male of 

 Calanus, mobile. Anterior antennee rather strongly built, the 2 basal segments 

 defined by a conspicuous constriction, the distal one the longer and consisting of 

 5 united articulations. Posterior antennse with the outer ramus consisting of 

 only 6 joints, the last very small, and having only a single seta. Anterior maxil- 

 lipeds quite rudimentary, knob-like. Posterior maxillipeds likewise much reduced, 

 terminal part indistinctly articulated and carrying behind 3 strong plumose setse, 

 in front only slight rudiments of bristles. Left leg of last pair with the terminal 

 joint a little shorter than either of the 2 preceding joints, somewhat lamellar, and 

 carrying on the tip 2 small unequal spinules. 



Colour. Body of femal pellucid with a bluish tinge, and often exhibiting 

 a broad transverse band of a dark red hue across the middle of the anterior 

 division. Body of male generally of a more uniform yellowish hue. 



Length of adult female scarcely exceeding 1 mm., of male about the same. 



Remarks. Dr. Giesbrecht is inclined to believe that the form observed 

 by Boeck might be different from Claus's species. This is certainly not the case, 

 as may be proved by comparing the figures here given with those of Glaus and 

 Giesbrecht. It is one of the smallest known Calanoids, and thus fairly deserves 

 its specific name. 



Occurrence. I have found this form rather plentiful in the Christiania 

 Fjord, as also off the southern coast of Norway. It does not seem to occur 

 farther noith, however; for Mr. Nordgaard, who has subjected the marine Copepoda 

 of the neighbourhood of Bergen to a careful examination, has not seen any speci- 

 men of this form, nor have I myself ever found it in the numerous samples of 

 plankton from the northern ocean that I have examined. It is generally met with 

 at the very surface of the water, both in the open sea and close to the shores, 

 not infrequently even in pools left by the tide. 



Distribution. The range of this Calanoid is pronouncedly southern and 

 quite extraordinarily wide, it having been recorded from the western part of the 

 Baltic, the North Sea, the British Channel, the western coast of France, the 

 Mediterranean, the Atlantic Ocean and the Pacific from Lat. 61 N. to 52 S. 



