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 Kroyeri Hansen. 



Head 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 (PI. 20, fig. 10). 



Thorax, ist segment in adult individuals about i Yg times as long as 

 the 2nd, in small individuals twice as long (PI. 20, fig. 7). The lengths of the 

 other thoracic segments vary greatly in different individuals (cf. PI. 20, figs. 

 7, 8 and 9). In adult specimens not filled with food and seen from above, 

 the 5th segment comes next to the 1st 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 (PI. 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 antennulae reach to about ^3 or V2 o^ ^^ 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. PI. 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. 9 a 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. 



1st maxillae (fig. 9 c, d, e and f). 2nd joint on the outer lobe in adult 

 male specimens strong and claw-like (fig. 9 c). Inner lobe cylindrical, with its 

 distal end generally somewhat swollen and knob-like. 



Immature specimens (fig. 9 e), 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- 



