REPORT ON THE ISOPODA. 6.3 



caudal shield measures 12 mm. in length by 12 mm. in greatest breadth in the male speci- 

 men, and 11 mm. in length by 11 mm. in breadth in the female ; it is therefore more than, 

 one-third of the length of the animal ; its shape is more or less hexagonal ; the lateral 

 portions are strongly bent down, and the uropoda come to be attached quite on the under 

 surface, and are almost invisible from above ; there is a median longitudinal keel which 

 bifurcates at about the end of the anterior fifth, on either side is a Y-shaped keel inclined 

 at an oblique angle ; the portion of the caudal shield which lies between the median and 

 lateral keels is flat, the part which lies outside the inner fork of the lateral keel is bent 

 downwards ; the posterior end of the caudal shield is slightly bent up. , 



AntenncB. — In the anterior pair the two first joints are short and about equal in size ; 

 the third joint is narrow and long, twice the length of either of the preceding joints ; the 

 fourth joint is very short ; the filament has about twenty-eight joints, each of which has 

 two sensory hairs ; the filament is nearly as long as the basal portion of the antenna. 



The second pair of antennae are longer; the filament has about twenty-one joints, and is 

 almost exactly equal in length to the last joint of the basal half of each of the antennae. 



The mandibles are like those of other species in being asymmetrical ; the left bears on 

 the upper surface a chisel-like process and above a single spine ; the right has two spines. 



The upper lobe of the Jirst pair of maxillce has ten spines upon its masticatory edge ; 

 the lower lobe has the usual form, and has but one slender spine close to the hinder 

 margin of the cutting edge. 



In the maxillipedes, the stipes and lamina are completely separated by suture ; the 

 margins of both are smooth ; the second joint of the palp is comparatively slender ; its 

 inner edge is beset with hairs along the distal half; close to the middle of the joint is an 

 oval prominence as in the other deep-sea species. 



One of the second pair of amhidatory limbs in the male is shown on PI. III. fig. 5. 

 The distal joint is as usual bent back upon the one in front like the blade of a closed 

 penknife upon its handle ; the penultimate joint is considerably broader at the base, and 

 bears about fourteen somewhat slender spines, arranged in pairs. 



The remaining ambulatory appendages (PL III. fig. 6) are slender, and but scantily 

 furnished with slender spines, some of which are serrated ; these are only to be found 

 at the distal extremity of the third, fourth, and fifth joints, and extending for a short 

 way along the outer margin of the fourth and fifth joints. 



The three anterior pairs of abdominal appendages have a tuft of two or three hairs 

 upon the projecting outer angle of the basal joint. 



The suture upon the operculum is at right angles. 



The uropoda are extremely small, and attached near the end of tlie lateral margins of 

 the caudal shield. 



Station 122c, September 10, 1873; lat. 9" 10' S., long. 34° 49' W. ; 400 fathoms; 

 bottom, red mud. 



(zooL. cn.u,L. EXP. — PART XXXIII. — 1884.) Kk 9 



