1908.] GENUS OF AMPHIPOD CRUSTACEA. 387 



Immature. The proportions are the same as in the adult. 



Young. First three pleon segments a little longer propor- 

 tionately than in adult, the plates rounded inferiorly, no trace of 

 lateral carina in second. 



Superior Antenna (PI. XVIIT. figs. 2 & 3). — In the acluU 

 female, the 1st joint of the peduncle is twice as long as the other 

 two taken togethei', broader than long, posterior margin concave, 

 cai-rying a series of auditoiy setfe distally ; the 2nd joint also 

 has three or four of these sette distally ; the 3rd joint is deeply 

 excavated anteiiorly for the insei-tion of the accessory flagellum. 



The primary flagellum consists of ten joints ; the 1st equalling 

 the first joint of the peduncle in length, and so broad as to appear 

 a continuation of it. It carries, on its anterior surface, a great 

 number of broad, hyaline, sensory filaments, arranged in two 

 longitudinal rows, about 22 groups of the filaments in each row. 

 The 2nd joint is short, widening distally, with a fringe of short 

 stiff setse at the anterior distal angle ; the 3rd joint is produced 

 at the antei-ior distal angle for the insertion of a long curved 

 spine which reaches nearly to the tip of the flagellum ; the 

 4th joint is cylindrical with a much shorter similar spine, and 

 with a transverse row of small set£e in the middle of the anterior 

 margin ; these three joints have each a row of setse inset midway 

 along the posterior margin. The following four joints decrease 

 gradually, each carrying at the distal anterior angle a fringe of 

 small setfe. The apical joint is very small, with one long stiff 

 bristle and two auditory setae. 



The accessory flagellum consists of one long laminar joint 

 and three small joints. The 1st equals in actual length the 

 first joint of the primary flagellum ; it carries three groups of 

 long setae on its upper mai-gin, with a group of six setfe at the 

 distal angle, two long, two short, and two "auditory." The 

 2nd joint is very small, cylindrical, rounded, with two long 

 sette and one auditory distally ; the 3rd is longer and more 

 slender than the second, slightly constricted in the middle, with 

 one long seta and one auditory; the apical joint is minute, 

 furnished with a long stiff bristle and three setse. 



As stated before, the numbei- of joints in the flagella of the 

 antennae appears to vary with the age of the specimen. In the 

 primary flagellum, the adult has 10, the immature 7, and the 

 young 4 ; in the accessory flagellum, the young form has only one 

 small joint, the immature specimen has two, and Boeck, Bovallius, 

 and Sars recoixl the numbei- as two for the adult, but in the 

 specimen here described there were three (fig. 3). The inferior 

 antennse also show this variation, the adult having 25, the others 

 10 and 4 respectively. 



In the immatm^e specimen (PI. XVIII. fig. 4) the 1st joint 

 of the peduncle is not so long in proportion as in the adult ; the 

 2nd and 3rd are subequal. taken together not so long as the 

 first. The primary flagellmn. has 7 joints; the first joint large 

 and stout, furnished with two i-ows of the sensory filaments, 



