TANAIDACEA AND MARINE ISOPODA FROM JUAN FERNANDEZ 545 
only have scattered setae on the telson and a few setae also in the lateral 
margins of the anterior part of the abdomen and in the hinder part of the thorax. 
Lamina frontalis as in Lanocira Kréyeri Hansen. 
Hlead about as long as the Ist thoracic segment. Apex between the 
antennae slightly rounded and equal in both males and females. Eyes large 
and black, seen from above subrectangular, but they extend over on the ventral 
side (Pl. 20, fig. 10). 
Thorax. ist segment in adult individuals about 1'/, times as long as 
the 2nd, in small individuals twice as long (Pl. 20, fig. 7). The lengths of the 
other thoracic segments vary greatly in different individuals (cf. Pl. 20, figs. 
7, 8 and g). In adult specimens not filled with food and seen from above, 
the 5th segment comes next to the Ist in length, but it is only slightly longer 
than the 4th and 6th. In specimens filled with food the 5th and 6th segments, 
seen from above, are extremely long, longer than the first, which is as long 
as the 7th. In young individuals, on the other hand, the 4th—7th thoracic 
segments are very short (Pl. 20, fig. 7). 
The coxal plates are subrectangular, with their posterio-lateral angles 
produced on the last 3 segments. They have a slight diagonal keel. 
Abdomen. Of the 5 anterior abdominal segments the Ist always, at least 
its largest part, seems to be hidden in dorsal aspect. In the specimens very 
full of food it is visible in lateral view. In the other specimen only 3 or parts 
of 4 of the segments are visible from above. 
The last abdominal segment has almost the shape of an equilateral tri- 
angle, but the lateral margins are slightly concave proximally and the apex is 
rounded and furnished with long setae and 6 small spines. 
Colour pale yellow, sprinkled with irregular dark brown dots of pigment. 
The anxtennulae reach to about 1/, or 1/, of the length of the last peduncu- 
lar joint of the antennae. In adult specimens they consist of 9 distinct joints; 
in the smallest specimens (about 3 mm long) there are only 7 joints (cf. Pl. 20, 
fig. 7). The peduncle consists of 3 joints, of which the first is a little more 
than twice as long as it is broad. 
The antennae reach beyond the middle of the 3rd thoracic segment. The 
peduncle is a little shorter than the flagellum. The first 3 peduncular joints 
are small, of about equal length and together about as long as the 4th joint. 
In the adult male the flagellum consists of 18 joints, in the adult female of 17. 
Immature specimens (length about 3 mm) have 13 joints. The sense organs 
on the flagellum are much longer in the male than in the female (PI. 20, figs. 
7 and 8). 
Mandibles (fig. ga and b). Equal on left and right sides. Apex biden- 
tate. Lacinia tooth-like and pointed. Molar flake-like and thin, generally with 
setae on the margins. 
Ist maxillae (fig. 9c,d,eandf). 2nd joint on the outer lobe in adult 
male specimens strong and claw-like (fig. gc). Inner lobe cylindrical, with its 
distal end generally somewhat swollen and knob-like. 
Immature specimens (fig. ge), as well as females with marsupium (fig. 9 d), 
have the 2nd joint on the outer lobe considerably shorter and slightly less 
curved. The inner lobe in immature specimens with narrow end. In one spe- 
