1908.] GENUS OF AMPHIPOD CRUSTACEA. 377' 



4tli are shorter and subequal ; the 5th is smaller again ; and the 

 6th and 7th are the shortest of all and subequal. All, except the 

 first, are produced at the posterior angles and rounded. 



Side-plates. — About half as deep as the body (see perseopod figs. 

 for the correct proportions. They are not well represented in 

 the figure of the whole animal owing to the immense distension 

 of the ovisac forcing them out of the normal position). The 1st 

 is small, triangular-, almost entirely covered by the large 2nd. 

 This side-plate is the largest of all, greatly dilated inferiorly and 

 produced forward, posterior margin straight. The 3rd is almost 

 as deep as long, with the anterior distal angle produced forward, 

 posterior margin straight, inferior margin rounded ; the 4th is 

 similar, but smaller ; the 5th and 6th successively smaller, 

 inferiorly bilobed ; the 7th is the smallest, subquadrate. 



Pleon. — First three pleon segments subequal, large, equalling 

 the first perpeonal segment in length. Epimeral plates large and 

 rounded, the 2nd and 3rd with a lateral carina which in the 2nd 

 terminates in a denticle at the posterolateral angle. The 4th 

 segment is deeply depressed dorsally ; the 5th is shorter than the 

 4th or 6th ; the 6th is depressed dorsally and emarginate for 

 the insertion of the telson. 



Superior Antenna. — Female (PI. XIY. fig. 3). The first joint 

 of the peduncle is as long as the two folloAving taken together, 

 broader than long, with a fringe of about 24 of the so-called 

 " auditory setse " around the distal posterior angle, and 8 smaller 

 similar setae in a cluster on the proximal posterior margin. 



The primary flagellum consists of one long broad joint and 

 eight small. The 1st joint nearly equals the peduncle in length 

 and is as long as the eight small joints taken together. It carries 

 on its inner surface two longitudinal bands of laminar hyaline 

 filaments (see fig.), about 38 ti-ansverse rows in each band. The 

 2nd joint widens distally and is furnished at the inner posterior 

 angle with a long, rigid, slightly curved spine reaching to the tip 

 of the flagellum ; the 3rd has a similar but shorter spine inserted 

 at the outer anterior angle. The 2nd, 3rd, 4th, 5th, and 6th 

 joints are all fringed on the inner mai-gin with a row of small, 

 stifi", curved setas, deeply inset ; the apical joint is tipped with two 

 long stifi" setse. 



The accessory fiagelluin is insei'ted anteriorly in a deep emargi- 

 nation of the peduncle and is composed of one long laminar joint, 

 and two small ones. 



The number and proportions of the joints appear to vary with 

 the age of the specimen. The 'Huxley' specimen, just described, 

 and one of the Irish sjjecimens, 20*5 mm. in length, have each 

 nine joints in the primary flagellum, with the first joint cylindrical 

 and swollen. The other two Ii'ish specimens, 20 mm. and 22 mm. 

 respectively, have eight joints, the first joint mvich more slender, 

 and incurved like that of the male, and the accessory flagellum 

 much longer in proportion. These two females appear to be 

 younger than the others — the claws and spines are much less worn. 



