28 THE VOYAGE OF H.M.S. CHALLENGEE. 



abdominal somites have eight keels each, including the marginal ones, and the sixth 

 abdominal somite has six. In all the abdominal somites the postero-lateral angles end 

 acutely in spines, as do the posterior ends of all the keels on the sixth and fifth, and all 

 except the submedians of the fourth. There are no median keels between the carapace 

 and the telson, but the third, fourth, and fifth abdominal somites have median tubercles. 

 The submedian keels of the fifth abdominal somite diverge posteriorly, while all the keels 

 of the sixth abdominal somite converge posteriorly. The first lateral keels of the first, 

 second, and third abdominal somites are slightly sinuous. The telson has a very prominent 

 median dorsal carina, which is situated upon the middle line of an elongated convex 

 protuberance. The carina ends posteriorly in a prominent acute spine, and it is bordered 

 by dark pigment at each end and in the middle. The margin of the telson carries six 

 acute spines, with a short dorsal carina running forwards from the base of each of them, 

 and a similar carina, without a spine, on the anterior portion of the latei-al margin. The 

 submedian spines are straight, the intermediate curved, and the externals curved and 

 very short. There is a single rounded lobe or tooth between the base of the external 

 spine and the base of the intermediate spine on each side, and eight on each side between 

 the base of the intermediate spine and the base of the submedian, and six between the 

 submedians, three of them on each side of the deep median notch, which is closed 

 behind and converted into a foramen in the single specimen which was obtained. On each 

 side of the broad median longitudinal ridge the dorsal surface of the telson is marked by 

 shallow pits symmetrically arranged in curved lines, running outwards and backwards 

 from the median ridge to the notches between the rounded lobes on the posterior border 

 of the telson. The ventral prolongation from the basal joint of the uropod ends in a 

 short curved outer branch, and a much stouter and longer inner branch which carries a 

 blunt rounded tooth on its outer edge about half way between the base and the tip, and 

 a number of irregular serrations along its inner edge. 



The outer edge of the second joint of the exopodite of the uropod is fringed by a 

 series of seven movable spines, the first six of which increase regularly in size towards 

 the tip, while the seventh is much larger than the sixth, and is terminal. The eye is 

 broadly triangular, and its length from its union mth the short stalk to the rounded 

 posterior angle of the cornea is about equal to its width between the two rounded angles 

 of the cornea, which is divided into two halves by a transverse vertical furrow. The 

 ocular somite is exposed on the middle line. The dactjdus of the raptorial second 

 maxilliped is divided into five curved acute teeth, and the keel on the anterior edge of 

 the third or carpal joint is smooth and entire. 



The movable ramus / (PI. 11. fig. 6) of the forceps on the first abdominal 

 appendage of the male is very large, and four times as long as the fixed ramus, which 

 is bent into a single hook at its tip. 



