REPORT ON THE ISOPODA. 131 



basal joints are short and subequal; the fourth joint is much loi ger, rather longer than 

 any two of the preceding, and curved; the distal joint is short. 



The chelipedes are stout and have the usual structure. 



Of the thoracic appendages the three posterior differ from the three anterior in having 

 the basal joint stout and swollen ; the three anterior pairs of ambulatory limbs are slender. 



All the abdominal appendages are present, and well developed. 



The uropoda are biramose, each branch consisting of two joints ; the outer branch is 

 more slender than the inner. 



Description of the Male. — The male specimens (fig. 1) are of about the same length 

 as the female. 



The cephalothorax is long and rather narrow, and is prolonged into a slight obtuse 

 process at its anterior extremity. The cephalothorax equals in length the first three 

 segments and half of the fourth segment. The eyes are large and oval. 



The first free segment of the thorax is the shortest ; the second segment is nearly 

 twice the length of the first ; the third is half again as long as the second, the fourth 

 and fifth are subequal, and about half again as long as the third ; the last segment of 

 the thorax is shorter than the fourth and fifth, and about as long as the third ; the 

 lateral margins of the segments are rounded, and the transverse diameter is greatest in 

 the middle and diminishes anteriorly and posteriorly, so that the segments are separated 

 by a well-marked constriction, the first free segment is separated from the cephalothorax by 

 a conspicuous notch, but it is not narrower anteriorly ; the last thoracic segment is closely 

 applied to the first abdominal segment, and is narrower anteriorly, but gradually increases 

 in width posteriorly. 



The abdomen equals in length the last two thoracic segments; the first five segments 

 are subequal in length and diminish imperceptibly in width from before backwards; the 

 terminal segment of the abdomen equals the two anterior in length ; it terminates in a 

 rounded extremity. 



The antennides (fig. 5) are about equal in length to the cephalothorax ; the basal joint 

 is long and stout, and much longer than the rest of the appendage ; the two following- 

 joints decrease progressively in length and in breadth ; the two distal joints of the 

 appendages are each somewhat longer than the third, but narrower. 



The antennas (fig. 5) are shorter and more slender than the antennules; the basal joint 

 is very short, the two following are somewhat longer and subequal ; the fourth joint is 

 much the longest and is about equal to the two last taken together; the appendage 

 terminates in two short slender joints which appear to represent the flagellum. 



The inaxillipedes are shown in fig. 6 ; each is furnished with a long four-jointed palp. 



The most characteristic appendages of the male Paratanais dimorphus are, however, 

 the chelipedes ; they appear to be not unlike the chelipedes of the genus Leptochelia in 

 general form, but are rather more massive ; this species, however, cannot be classed in the 



