38 R. NORRIS WOLFIiNDEN. 



IIETEROKRHABDUS (Giesbrecht). 



( )iily one specimen of this genus occurs in the ' Discovery ' collection, which is 

 only what might be expected from the fact that the collection is practically only 

 epiplanktonic, whereas Heterorrhahdus is without doubt one of the most confirmed deep- 

 water genera of Copepoda. The species H. austrina (Giesbrecht), which occurs in the 

 ' Belgica ' and ' Gauss ' collections, is absent from those of the ' Discovery,' and the only 

 specimen of the genus occurring in the latter is, I think, referaljle to //. lonfficornis. 



Heterorrhabdus longicornis. 



Beterochceta longicornis, Giesbrecht. Atti. Ace. Line. Rend., Ser. 4, v. (1889) p. 811. 

 „ ., „ Fauna u. Fl. Neap. XIX. (1892), p. 373. 



Wolfenden. Jour. Mar. Biol. Assoc., Vol. VII. (1904) p. 124. 

 / Heteroclueia major, Dabl. Verb. d. Zool. Gesells., 1894, p. 79. 

 Heterorliahdus major, Wolfenden. Plankton Studies, Part I. (1905), p. 11. 



I first described the male of H. longicornis, hitherto unknown, in 1902. Since 

 then I have found it frequently throughout the Atlantic, extending to the Antarctic 

 area. Dahl's description of //. mnjor is very scanty, and the only essential point of 

 difterence between it and longicornis appears to be one of size. The specimen in the 

 ' Discovery ' collection is a $ of 4*5 mm. length, but there is no essential difterence 

 between it and smaller males from the Faroe Channel. I suggest therefore that Dahl's 

 H. major is really //. longicornis, and I now think that the species which I described in 

 " Plankton Studies " as //. major may best be described as H. longicornis (Giesbrecht). 



The diagnostic points of H. major (Dahl) are, according to this author, " anterior 

 antennae very long, the posterior foot-jaw with only weak median bristles ; the 

 penultimate lobe of the anterior foot-jaw a long ' tap ' lobe, the mandible teeth but 

 little differing in thickness, nearly the same distance apart ; the exopodite of the third 

 feet like those of the second and fourth, the size over 5 mm. long." 



Except as to size, it will be observed that none of these points diff'er from those of 

 //. longicornis, the largest examples of which are not, however, more than 3 • 5 mm. long 

 in the North Atlantic. 



The ' Discovery ' specimen is a $ of 4 • 5 mm. length, the anterior antennae several 

 joints (about six) longer than the whole body ; the geniculating antennas with six 

 joints beyond the elbow. The right furcal segment is much longer than the left. The 

 fifth lobe of the anterior foot-jaw has a very thick-based stout curved hook, without 

 teeth or bristles except for a few bristles at the proximal end ; the lobe itself is very 

 large. The two other bristles are long and thin. The sixth lobe has a long and thin 

 hook, also uncombed. The bristles of Ri are extremely long. The posterior foot-jaw 

 has a long thin second basal, three times as long as broad, and only two weak bristles 

 in the middle. The mandil)le has a large simple conical tootli on the outside, and 



