38 
R. NORRIS WOLFENDEN. 
HETERORRHABDUS (Giesbrecht). 
Only one specimen of this genus occurs in the c Discovery ’ collection, which is 
only what might be expected from the fact that the collection is practically only 
epiplanktonic, whereas Heterorrhabdus is without doubt one of the most confirmed deep- 
water genera of Copepoda. The species II. ausirina (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, referable to II. longicornis. 
Heterorrhabdus longicornis. 
Heterochceta longicornis, Giesbrecht. Atti. Acc. Line. Rend., Ser. 4, v. (1889) p. 811. 
„ ,, „ Fauna u. FI. Neap. XIX. (1892), p. 373. 
„ „ Wolfenden. Jour. Mar. Biol. Assoc., Yol. VII. (1904) p. 124. 
? Heterochceta major, Dahl. Verb. d. Zool. Gesells., 1894, p. 79. 
HeterorhaMus 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 II. major is very scanty, and the only essential point of 
difference 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 difference 
between it and smaller males from the Faroe Channel. I suggest therefore that Dahl’s 
H. major is really II. longicornis, and I now think that the species which I described in 
“ Plankton Studies ” as H. major may best be described as II. 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 differ from those of 
II. 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 antennae 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 mandible has a large simple conical tooth on the outside, and 
