HANSEN: THE ISOPODA. 119 
Abdomen. It occupies less than one third of the length of the animal, and 
the segments are well separated on the dorsal surface. The pleural plates are 
very large and lamellar, partly overlapping one another, in the first segment 
somewhat longer than those of the last thoracic segment, and then gradually 
increasing in length and turning more backward from the first to the fifth seg- 
ment. The ventral side of the five anterior segments about as in the preceding 
species. Each pleopod with two triangular or ovate rami of medium size ; the 
pleopods decrease somewhat in size from before backward, and the outer ramus 
is as a rule a little smaller than the inner one. Hach uropod consists of one 
ramus (Fig. 25) which is oblong-ovate and considerably smaller than the 
pleural plates of the fifth abdominal segment. 
Size. The largest specimen is 10.4 mm. long to the apex of the sixth ab- 
dominal segment, 11.8 mm. to the end of the uropods, and 7.4 mm. broad. 
The smallest specimen — with eggs in the marsupium — is only 7 mm. long to 
the end of the abdomen, and 5.8 mm. broad. 
b. Male. 
The body is very elongate (Fig. 2f), between 3} and 4 times longer than 
broad. 
Head. The dorsal surface is convex, the antero-lateral margin much curved, 
and the anterior part of the head bends somewhat downward. Eyes could not 
be detected, but we find small frontal impressions, which vary very much in 
different specimens (in one specimen two pairs were found). The antennule 
(Fig. 29) of medium length, 3-jointed ; the basal joint thick and almost glob- 
ular, the second shorter and much narrower than the first, the third minute. 
The antenne of medium length, 5-jointed ; the first joint thick and almost glob- 
ular ; the three following joints gradually a little shorter and much narrower; 
the apical joint minute. The labrum extremely broad, crescent-shaped. The 
hypopharynx reaches to the middle of the labrum; it is rather long, of medium 
breadth, tapering somewhat towards the rounded end. Mandibles, maxillule, 
and maxille (f) normal ; the maxilliped (g) has the shape of a rather small 
oblong triangle. 
Thorax. The fifth segment is the broadest, a little broader than the seventh, 
and considerably broader than the first segment. The lateral outline of the 
segments either rounded or (Fig. 2f) more straight with rounded angles ; the 
incisions between the segments narrow, triangular, and very deep, The ventral 
surface without conical protuberances. The legs more slender than in the pre- 
ceding form; from before backward to the fifth pair they increase a little in 
length and their hand in size, and from the fifth to the last pair at least the 
hand decreases somewhat in size. In Figure 2h is shown the left leg of the 
first pair, and in Figure 2% that of the seventh pair. 
Abdomen. It occupies about two fifths of the total length of the animal, 
and decreases in breadth from before backward to the small square sixth seg- 
ment. All segments are very movable; seen from above, their lateral portion 
in the large specimen is triangular with the lateral angles more or less acute, 
