IgI5.] T. SouTHWELL : Indian Parasites of Fish. 321 
(7) Description of a new species of Isopod Crustacean 
parasitic on the Bhekti-(Lates calcarifer). 
Rocinella latis, n. sp. 
(Plate xxviii, figs. 12-15). 
No. 2985 From skin of Lates cal- | Diamond Harbour (R. —_T. Southwell. 
carifer, 15-11-1915. Hughli), near Cal- 
cutta. 
All the specimens caught were males. The head projects well 
beyond the basal joints of the first and second antennae as a 
broadly rounded plate, convex from above. The first peraeon 
segment is longer than the rest. The first five segments of the 
pleon are a little narrower than those of the peraeon. The telson 
is slightly narrower than the preceding segments of the pleon. 
The eyes are large, well separated, and situated laterally. 
They extend on to the ventral surface. 
The bases of the first and second antennae are hidden in dor- 
sal view by the frontal lamina which extends well beyond them. 
The first antennae are much stouter and much shorter than the 
second antennae. The flagellum is 8-jointed and terminates ab- 
ruptly. The last joint extends to the middle of the first peraeon 
segment. ‘The second antennae are, as noted, slender. 
The flagellum consists of Io (possibly 11) joints and it extends 
to the posterior extremity of the first peraeon segment. In length 
it exceeds that of the first antennae by its terminal 3 joints. The 
basal joints of the antennae are not distended. 
The upper lip is crescentic, thin and membranous. 
The mandibles have the palp somewhat elongated. 
The first three pairs of legs are prehensile and have long and 
evenly curved dactyli, the extremities of which are of a dark 
brown colour in most specimens. The propodus is broad and 
crested and is armed with about 8 long, pointed, comb-like spines. 
There is a single elongated spine at the distal and exterior angle 
of the merus. The spines on the propodus of the first pair of 
legs are not quite as well defined as those of the second and third 
pairs. 
The four gressorial legs are very similar to the first three pairs 
of legs, but a little more slender. The dactylus bears two spines 
near its base. The propodus bears 8 spines, but the spines are not 
borne on a crest, z.e. the propodus is not nearly so broad as is the 
case in the first three pairs of legs. The carpus bears four spines 
and the merus two. All these spines are situated on the internal 
surface. The last pair of legs is slightly smaller than the rest. 
The largest specimen measured 14 mm. long and the greatest 
breadth was 4°5 mm. 
In young specimens the whole surface is marked with minute 
pigment spots, hardly visible to the naked eye. In adults, how- 
ever, the pigment consists of three very narrow longitudinal bands, 
one on each side and one running along the centre of the carapace. 
