1G5 
So far as my knowledge goes, the division of the exopodite of 
all the pleopoda except the first, into two distinct joints is very 
unusual in the Isopoda; the plate attached to the outer margin 
of the base (epipodite ?) also appears to be peculiar to this genus 
The Uropoda (Plate xxv., fig, 6) are well developed and extend 
somewhat beyond the extremity of the pleon. The basal joint is 
as long as the longer of the two rami and is very stout ; on the 
under side near the base it bears two groups of stout setae, each 
group containing about six or seven. The upper surface is broad 
and slightly concave, each of the edges being supplied with a row 
of stout spiniform setae, which are more numerous on the outer 
than on the inner edge, and are largest towards the distal end. 
At the end of the base below the articulation of the outer branch 
are two very thick setae with a few pectinations at the end on the 
upper side only. Many of the other stout setse on the uropoda 
are pectinated in the same way though not to the same extent. 
The two rami are similar, subcylindrical in section, tapering 
distally and curving slightly upwards. The inner is slightly the 
longer, both bear stout setae and a larger number of fine setae or 
hairs arranged in groups chiefly on the upper surface ; the ends 
of each are free from setse. 
Sexual differences . — Of the specimens I have examined, nearly 
two-thirds were undoubtedly males, all having the external male 
organs present at the base of the seventh pair of thoracic legs. 
One of these is shown in Plate xxvi., tig. 6. The remainder of the 
specimens were females. They are similar in general appearance 
to the males but are slightly smaller, the subchelate hand of the first 
pair of thoracic legs is less strongly developed, the fourth pair of 
thoracic legs does not present the special modification found in 
the male, and the second pair of pleopoda are of normal form. 
None of the specimens examined bore eggs or young, but some 
had what appeared to be small brood plates already developed on 
the bases of the legs of the second, third and fourth segments of 
the pereion. 
Position of Phreatoicus among the Isopoda. 
When I originally described the genus Phreatoicus in 1882 I 
in fig. 5. Besides these bodies I have found on other pleopoda great 
numbers of other bodies which appear like empty spherical cases with a 
small oblong or elliptical opening — many of them being broken or im- 
perfect. I have not the least idea what they may be, but they are so 
numerous on the pleopoda of some specimens that I thought it best to 
mention them. They appear merely to rest on the surface of the pleopoda 
but whether their presence there is accidental or not I cannot say. A 
small stalked Infusorian (Vorticella? ) is also found in great abundance 
attached to the hairs of the pleopoda, three or four individuals usually 
branching from the one stalk. 
B— July, 1891. 
