121 



HeterorhaMus, apical spine slender, setiform. Last pair of legs in female resem- 

 bling in structure the preceding pairs, but of inferior size, 2nd joint of outer 

 ramus without any falciform spine inside; those in male with the outer rami 

 imperfectly prehensile. 



Remarks. This genus was established by Glaus in the year 1863, to 

 comprise some Mediterranean Calanoids distinguished by the extraordinary pellu- 

 cidity of the body, and the richly plumose setse with which some of the appendages 

 were ornamented. The generic name proposed, Hemicalanus, had however previ- 

 ously been used by Dana in a different sense, and for this reason it has recently 

 been replaced by Dr. Giesbrecht with that of Haloptilus. Two of the species 

 described by Glaus as belonging to this genus have moreover been transferred 

 by the same author to another nearly-related genus, Augaptilus, Giesbr. In the 

 restriction now generally adopted, the present genus is easily recognized by 

 the perfectly hyaline, sub-depressed body, the comparatively short urosome, the 

 exceedingly slender anterior antennae, and the greatly produced inner ramus of 

 the posterior ones. Moreover the structure of the oral parts is rather charac- 

 teristic. We know at present of 11 or 12 species belonging to this genus. They 

 are, on the whole, southern in distribution. 6 of the species occurring in the 

 Mediterranean, the others in the Pacific and the tropical part of the Atlantic Ocean. 

 Two of the species, however, have been stated to occur occasionally in the Nor- 

 wegian Sea, one of them even as far north as in the Polar basin crossed by Nansen. 

 These 2 species, which can thus only be regarded as quite exceptional visitors 

 in the northern ocean, will be described below. 



52. Haloptilus longieornis (Glaus). 



(PI. LXXXII & LXXXIII, fig. 1). 

 Hemicalanus longicornis, Glaus. Die freilebenden Copepoden, p. 179, PI. XXIX, fig. 1. 



Specific Characters. Female. Body rather slender and distinctly depressed, 

 with the anterior division, seen dorsally, oblong fusiform in outline, - greatest width 

 scarcely exceeding y s of the length, and occurring about in the middle, anterior 

 extremity somewhat contracted, though slightly widening at the insertion of the 

 anterior antenna, and projecting in the middle to a knob-like prominence, posterior 

 extremity considerably narrowed. Cephalosome about the length of the metasome 

 and genital segment taken together, rostral prominence obtuse, and occurring not 

 far from the frontal edge; tentacular filaments very delicate. Last segment of 

 metasome with the lateral parts not at all expanded, Urosome scarcely exceeding 



17 Crustacea. 



