38 THE VOYAGE OF H.M.S. CHALLENGER. 



smaller and not so slender, the setae stouter than in the female, shorter, and recurved. 

 The four pairs of swimming feet are very short, nearly alike, the inner branches about 

 half the length of the outer, and three-jointed, except in the first pair, where they have 

 only two joints. The fifth pair is absent in the female, but in the male exists in the 

 shape of two small, unequal, simple prehensile limbs (PL II. fig. 10). The abdomen 

 is extremely short, scarcely more than one-sixth or one-seventh of the length of the 

 cephalothorax. The second tail-seta, on the left side only, is much longer than the rest, 

 and is about equal to the length of the body of the animal. 



I have seen two species referable to this genus, both of which occurred in considerable 

 numbers in several of the Challenger gatherinsrs. 



In his great work on the Crustacea of the United States Exploring Expedition, Prof. 

 Dana remarks respecting Calanus attenuatus, that "the multiarticulate character of the 

 smaller branch of the posterior antennae may authorise the institution of a new genus, or 

 sub-genus, for this and allied species, for which we propose the name Eucalanus. The 

 above species will be Eucalanus attenuatus." And though Dana does not himself adopt 

 that suggestion, but calls the species Calanus attenuatus, it yet seems to me that the 

 name proposed by him, though in this hesitating way, may fairly claim precedence over 

 the later generic term of Dr. Claus. I therefore accept Eucalanus as the proper name of 

 the genus, which was very rightly separated by Claus from Calanus, on account not only 

 of the general peculiarity of its external form, as shown in the peculiarly attenuated head, 

 very long body, and stunted abdomen, but also on account of the abnormal structure of 

 the antennae, mandible-palp, and posterior foot -jaws, together with the absence of a fifth 

 pair of feet in the female. These characters are certainly amply sufficient to sustain 

 " Calanella " as a distinct generic form. And it seems pretty clear, as pointed out by Claus, 

 that some species of " Calanus" described by Dana and Lubbock (e.g., Calanus elongatus, 

 Dana; Calanus attenuatus, Dana; Calanus dance, Lubbock; and Calanus mirabilis, 

 Lubbock) belong to " Calanella." 



1. Eucalanus attenuatus, Dana (PL VI. figs. 1-8, and PL II. figs. 8-10). 



Calanus elongatus, Dana, Crust. IT. S. Expl. Exped. (1852), p. 1079, pi. lxxv. fig. 1. 



Calanus attenuatus, idem, ibidem, p. 1080, pi. lxxv. fig. 2. 



Calanus ut i nihil Is, Lubbock, Trans. Entom. Soc, vol. iv. (1856), pi. v. figs. 1-6 ; and Trans. 



Linn. Soc, vol. xxiii. p. 178, pi. xxix. fig. 1. 

 Calanella mediterr a nea (1), Claus, Die frei lebenden Copepoden (1863), p. 176, pi. xxviii, figs. 6-11. 



Length, 1-Gth of an inch (4"2 mm.). Rostrum small (PL VI. fig. 3), divided at 

 the apex into two long and slender, thread-like filaments. Anterior antennae twenty- 

 three jointed, about one-third longer than the body, sparingly setiferous, but bearing 

 numerous short club-shaped appendages ; seventh joint longer than those immediately 

 preceding or following it ; the last joint armed with three or four, the penultimate and 



