REPORT ON THE ISOPODA. . 125 



terminates in the middle line in a very short, blunt rostrum ; on either side of the 

 shallow excavations which lodge the basal joints of the anteunules are the minute but 

 separate ocular lobes ; these are rounded, oval in front, the anterior end being pointed and 

 prolonged ; there was no trace of any ocular structures. The first free thoracic segment 

 is shorter, rather more than half the length of the four succeeding segments, which are 

 subequal ; the last thoracic segment is shorter than the foregoing ; each of these segments 

 is rather narrower anteriorly where it articulates with the segment in front ; the general 

 shape of the segment is short, oblong, with rounded angles ; this does not apply to the 

 first or to the last free segment of the thorax, which are broader than they are long. 



The five anterior segments of the abdomen are equal in length and in diameter, only 

 the first one being a trifle longer than the rest. 



The terminal segment of the abdomen is longer and wider than the rest ; it has a 

 pair of lateral projections with which the uropoda articulate ; posteriorly it is rounded 

 and a minute median triangular process projects from the extremity ; on either side of 

 this the posterior margin of the abdomen is slightly concave. 



The antennules (fig. 5) are considerably stouter than the antennae ; the peduncle has 

 three joints, of which the proximal one is much the longest and stoutest ; it is furnished 

 with a tuft (three or four) of slender spines on the outer side, near to its articulation 

 with the second joint; the second joint is about one-fourth of the length of the first, 

 and like it has a tuft of slender spines occupying a similar position to those of the basal 

 joint, and one slender hair-like spine upon the opposite side ; the third joint of the 

 peduncle is stouter again, with one or two short slender spines upon the inner as well as 

 the outer margin, just before its articulation with the flagellum ; the latter consists of 

 four joints, of which the first is very much the longest, as well as broader than the 

 succeeding joints ; each of the three distal joints is furnished with a single olfactory hair. 



The antennie (fig. 6) are considerably more slender and shorter than the antennules ; 

 the peduncle consists of five joints ; the basal joint is short and oval, much stouter than 

 any of the succeeding joints, which are of equal thickness ; the second joint is moderately 

 long, the third stouter, the fourth and fifth subequal to each other and to the second 

 joint ; the flagellum has four joints, which decrease gradually in diameter, the first being 

 the widest ; the first joint of the flagellum is also the longest, the two middle ones are 

 shorter and subequal, the fourth shorter still, and provided at its extremity with a tuft 

 of fine hairs. 



As the only specimen was mounted on a slide in Canada balsam it is impossible to 

 describe, in a detailed manner, the mouth appendages, which do not appear, so far as 

 could be seen, to present any marked differences from those of other species. 



The chelse are short and very stout ; the second joint is particularly stout as com- 

 pared with the others ; the third joint as usual is very small, a portion of the fourth 

 coming to articulate directly with the second ; in the fifth joint the palm is 



