72 THE VOYAGE OF H.M.S. CHALLENGES. 



One specimen only was found amongst the Copepoda from Zebu Harbour, Philippine 

 Islands. The parts were not very clearly made out on dissection, but so far as appears, 

 the individual is not referable to any known species. 



Acartia, Dana. 



Acartia, Dana, Amer. Journ. Sci., 1846. 

 Bias, Lilljeborg, Crust, ex. ord. trib., 1853. 



„ Claus, Die frei lebend. Copep., 1863. 



,, Boeck, Oversigt Norges Copepoder, 1864. 



„ Brady, Monog. Brit. Copep., 1878. 



Body long and slender, head produced into a slender rostrum, abdomen composed in 

 the male of live, in the female of three, segments. Anterior antennas in the female 

 twenty -jointed, bearing scattered long setse, nodose, and in the male, on the right side, 

 geniculated. External branch of the posterior antenna long, three-jointed ; internal 

 branch short, one-jointed. Labium very large, three-lobed, setiferous, the middle lobe 

 very broad. Mandible-palp of moderate size, two-branched, branches short, one- or two- 

 jointed. Anterior foot-jaws large, bearing numerous uncinate setse, which are pectinated 

 as in Pontella; posterior composed of a broad basal, and a more slender apical portion ; 

 the basal part provided with four or five very long plumose setse, the apical part 

 sparingly aculeate. Internal branches of the swimming feet two-jointed, outer branches 

 three-jointed. Fifth pair of feet one-branched, prehensile in the male, in the female 

 rudimentary, consisting of a small basal joint, from which spring two slender, unequal 

 setse. Eye mobile, formed of several lenses. 



The genus Acartia, though very imperfectly characterised and figured by Dana, was 

 evidently meant to include the species belonging to Lilljeborg's more recently established 

 genus Dias. Dana, however, does not appear to have seen the male of any of the four 

 species described by him ; and this accounts for his guarded statement as to the non- 

 geniculation of the male antennse. Indeed the males of the pelagic species of Acartia 

 seem to be very scarce. I carefully hunted for them in all the gatherings which have 

 come under my notice, and only found one example, — a remarkable fact, seeing that in 

 any gathering of the well-known European species, Acartia longiremis, males are quite 

 commonly met with. The geniculation of the right anterior male antenna is rather in- 

 distinct, but the limb is considerably swollen for the insertion of flexor muscles ; the 

 posterior antenna has on the second joint of its larger branch a marginal series of rather 

 long hairs. The marginal spines of the swimming feet differ from the common type in 

 being continuous with the joints of the limb, and not articulated appendages. The 

 terminal spines are narrow, sword-shaped, and finely serrated, and in length are more 

 than equal to the whole outer branch. 



