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



of the species in some other respects ; considering also that I have met with no gathering 

 of the adult form in which the gracile form does not also occur, and that Dr. Claus like- 

 wise found both forms in the Mediterranean, — I yet adhere to the belief that a thorough 

 study of the development and morphology of the animal will show these two debateable 

 forms to be but varieties of one and the same species. It is perhaps worth noting that 

 the only females which I have seen with attached spermatophores occurred in one or two 

 gatherings containing males which had the distorted abdomen. 



Habitat.— -Lat. 47° 25' S., long. 130° 12' E. ; off Port Jackson; off Cape Howe, 

 Australia ; off Kandavu, Fiji ; off the Ki Islands ; between Api and Cape York ; Pacific, 

 north of the Sandwich Islands; South Pacific, lat. 40° 3' S., long. 132° 58' W. ; and off 

 the west of Patagonia ; lat. 36° 44' S., long. 46° 16' W. ; lat. 37° 45' S., long. 33° 0' W. ; 

 Atlantic from lat. 5° N. to 2° N. ; and about lat. 26° N., near Station 353 ; in lat. 36° 

 32' S'., long. 132° 52' W. (Station 287) ; in lat. 64° 37' S.,long. 85° 49' E. (Station 154) ; 

 in lat. 37° 17' S., long. 53° 52' W. (Station 320). 



Heterochceta, Claus. 

 Heterochceta, Claus, Die frei lebenden Copepoden, 1863. 



Body attenuated behind, abdomen of the male five-, of the female four-jointed. 

 Anterior antennae twenty-five-jointed ; that of the left side in the male feebly geni dilated. 

 Colouring matter of the eye entirely wanting. Posterior antennae as in Calanus. 

 Anterior branch of the maxilla obsolete. Anterior pair of foot-jaws very stout, armed 

 with strong curved and partly pectinated setae ; posterior foot-jaws slender, nearly as in 

 Calanus. Fifth pair of feet two-branched, those of the female like the preceding pairs, 

 except that the outer branch bears a very long divaricate spine at the apex of its second 

 joint ; in the male the outer branches are prehensile and slightly different on the two 

 sides. The left caudal stylet bears one excessively long seta. 



Heterochceta, though abundantly distinct from any other described genus, presents 

 some interesting points of resemblance, especially to Candace, Leuckartia and Pleu- 

 romma : — to Candace in the powerfully formed posterior foot-jaw, to Leuckartia and 

 Pleuromma in the general build of the swimming feet and of the anterior antennae. 

 But the remarkably long seta of the left caudal segment, the absence of the internal branch 

 of the maxilla, the characters of the fifth pair of feet in both sexes (which come nearer to 

 Centre-pages than to any other genus), together with the very slightly deformed left 

 anterior antenna of the male, constitute a sufficiently distinctive series of generic 

 characters. 



