TANAIDACEA AND MARINE ISOPODA FKOM JUAN FERNANDEZ 535 



Abdotnen. Besides the telson, 6 abdominal segments are to be seen. 

 The first 4 segments are of about equal length, but the 5th segment is about 

 twice as long as the 4th. The 6th segment does not reach the lateral sides 

 of abdomen and is situated between the bases of the uropods. It is of about 

 equal length to the 5th, has its posterior margin cleft and a deep longitudinal 

 dorsal furrow in the middle line. The segments are well limited, but dorsally 

 a little less distinct. 



Telson, fig. 5 a, linguiform, narrower at the base, slightly tapering to the 

 narrowly rounded setiferous end. Dorsal side of telson almost flat, at the base 

 with a very faint longitudinal groove surrounded by two slight keels. Ventral 

 surface basally with a very faint longitudinal keel, which gradually disappears 

 on the proximal half. Distal half almost flat. 



Colour pale yellow with scattered, rounded, dark brown dots. 



Antennulae about as long as the head. They reach a little past the 

 proximal margin of the ist joint of the flagellum of antennae. First joint 

 about as long as the two following together, 3rd joint a little longer than the 

 2nd. The flagellum is about as long as the peduncle and consists of 8 joints, 

 of which the last is very minute. 



Antennae. The peduncle consists of 5 joints. The ist peduncular joint 

 is about 7$ as long as the 2nd, which is a little broader. At its outer side it 

 is thin and blade-like and has its margin a little convex. Inner margin nearly 

 straight. The 3rd joint is only about half as long as the 2nd. The 3rd, 4th 

 and 5th joints increase in length, so that the 5th is about twice as long as 

 the 3rd. The flagellum is about as long as the 4th peduncular joint. Three 

 very obscure, minute apical joints are slightly indicated. The relation between 

 the iengths of the peduncular joints and the flagellum is 12:17:6.5:11:13:11. 



Mandibles. Apex awl-like, acute. The palp consists of 3 joints. 2nd 

 joint the longest, furnished with one seta at the lower distal angle. First joint 

 a little more than half of the length of the 2nd. 



ist maxillae. 2nd joint with about 12 saw-like teeth. 



2nd maxillae coalesced with the lower lip (cf. Stebbing, 1896), distally 

 a little widened. 



Lower lip distally deeply cleft into two lobes with their ends acute. 



Upper lip triangular, with acute apex. 



The maxillipeds are characteristic of the genus but have a very minute 

 terminal joint. 



ist pereiopod (fig. 5 b). Second joint a little longer than the 3rd; 6th 

 joint ovate, ventrally with a furrow for the claw. On both the posterior and 

 the anterior side there is one submarginal row of setae near the lower margin. 

 The ordinary tooth on the lower margin next the carpus is vestigial. Anterior 

 edge slightly convex, posterior edge almost straight. 



2nd and jrd pereiopods (fig. 5 c). Propodus with a row of 10 strong 

 and a great many slender setae on the lower margin. 



4th— yth pereiopods (fig. 5 d). 4th joint with the upper distal margin 

 produced and pointed and furnished with a seta in the apex. 5th joint with 

 the upper distal part not produced, furnished with 5 broad setae on the 

 lower margin; the longest seta in the lower distal angle. 6th joint with 5 

 .strong setae on the lower margin. For other details see the figure. 



