BEPORT ON THE COPEPODA. 45 



2. Hemicalanus orientalis, n. sp. (PI. IX. figs. 8, 9, and PI. X. figs. 1-4). 



Anterior antennae (PL X. fig. 1) as long as the body, slender, and rather densely 

 clothed with long setae. The rostrum is long and slender, and the swimming feet much 

 more robust than in the preceding species. One specimen only was found. Length, 

 l-9th of an inch (2*8 mm.). Male unknown. 



Habitat. — Between Arrou and Banda. 



3. Hemicalanus aculeattts, n. sp. (PL XLVI. figs. 2-4). 



Length, 23-100ths of an inch (5"75 mm.). Forehead produced and sharply aculeated, 

 body subcylindrical, cephalothorax six or seven times as long as the united lengths of 

 abdomen and furca. Anterior antennas longer than the body, twenty-five-jointed, basal 

 joints short and clothed with plumose hairs, distal joints much more slender and bearing 

 non-plumose setae. Secondary branch of the posterior antenna long, six -jointed, and 

 bearing very long plumose hairs, those of the primary branch non-plumose. Four pairs 

 of swimming feet, which have all the branches three-jointed, the outer branches of all 

 except the first pair bearing beautifully plumose setae. Abdominal segments, except the 

 first, extremely short ; caudal lamellae subquadrate, not much longer than broad and 

 slightly divergent ; setae five, the outer about half as long as the inner, all densely 

 plumose, the longest about twice the length of the abdomen. The proximal halves of 

 the setae throughout the body are usually either destitute of plumes or have them 

 only slightly developed ; colour of the plumes smoky brown. 



I have seen only one specimen of Hemicalanus aculeatus, which was mounted during 

 the cruise and labelled " Deep haul, 23rd July 1875, Pacific." The drawing of the 

 whole animal given in PL XLVI. was taken from the mounting, and shows all that I could 

 make out of the details before dissection. 



Pleuromma, Claus. 



Pleuromma, Claus, Die frei lebenden Copepoden, 1863. 

 Metridia, Boeck, Oversigt af Norges Marine Copepoder (1864). 

 ,, Brady, Monog. British Copepoda, 1878. 



Head distinct from the thorax; fourth and fifth segments of the thorax coalescent; 

 abdomen composed in the male of five, in the female of three segments. Anterior 

 antennae twenty-five- jointed in the female, that of the left side in the male twenty - 

 three-jointed, 1 that of the right side nineteen-jointed and geniculated between the 



1 In some cases the eighth and ninth articulations of the left antennas are distinctly marked, and this condition is 

 shown in the plate. 



