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



widely distributed, it does not appear that the genus is rich in species ; only two others 

 have been found amongst the Challenger captures, and these occurred but sparingly. 



1. Centre-pages brachiatus, Dana (PI. XXVI. figs. 1-7). 



Calanopia Irachiata, Dana, Crust. U. S. Expl. Exped., p. 1133, pL Ixxix. fig. 7, a.b. 



Length, 8-100ths of an inch (4 - 4mm.). Cephalothorax elongated, slightly constricted 

 at the points of junction of the somites, posterior angles produced into strong hook-like 

 spines ; anterior antennas slender and about equal in length to the body of the animal, the 

 first two joints somewhat larger and stouter than those immediately following, those from 

 the third to the eleventh very small, none of them being much longer than broad, the 

 next three considerably longer ; the fifteenth to the nineteenth are the longest of all, 

 being about four times as long as broad, the apical joints somewhat shorter ; the entire 

 limb beset with rather short, slender setse ; the first, second, and fifth joints each bear 

 on the outer margin a short, stout spine, and several of the lower joints, from about the 

 seventh to the twelfth, have one or more aborted spines (fig. 2). The right anterior 

 antenna of the male (fig. 3), in addition to the spines already mentioned, has well- 

 developed spines on the tenth and eleventh joints ; the twelfth, thirteenth, and four- 

 teenth are greatly enlarged, the thirteenth and fourteenth having each a very strong 

 spine ; the fifteenth, sixteenth, and seventeenth joints are more slender, but about 

 twice as long as the preceding, and are armed on the inner aspect with finely serrated 

 plates, the hinge being situated between the sixteenth and seventeenth ; the eighteenth 

 joint is of equal size, but has no serrated plate ; these four joints represent by coal- 

 escence seven joints of the normal antenna (15-21). The outer branch of the fifth 

 foot in the female has the middle joint very short, and produced internally into a very 

 long and strong spine, the margins of which are smooth. The outer branch of the 

 right fifth foot in the male (fig. 6) forms a powerful, doubly-clawed, prehensile organ, 

 the upper internal angle of the middle joint produced into an extremely long hooked claw, 

 which opposes at its extremity the claw -like termination of the last joint ; the lower 

 outer angle also of the middle joint forms a long claw-like process, which is twisted to 

 the inside so as to have the same direction as the upper claw ; the foot of the left side 

 has the outer branch two-jointed, equal in length to the inner branch, the last joint 

 truncated, and bearing only three or four setae at the apex. The first segment of the 

 female abdomen has on each lateral margin two slender curved spines. The caudal seg- 

 ments are about twice as long as broad, and likewise twice as long as the last abdominal 

 segment. Tail setse subequal, short, the longest considerably shorter than the length of 

 the abdomen, the four external setse in the female, but not in the male, are conspicuously 

 dilated towards the base. Eye small, composed of two closely approximated ocelli. 



Habitat. — Several specimens of this species occurred in tow-net gatherings off 



