AMPHIPOD GENUS LEPTOCHEIRUS. . 565 



darkly pigmented in the centre of the eye ; the outer ring in 

 the young animal is quite colourless, though this, of course, may 

 only be due to the fading of the pigment, little of which is left in 

 Zacldach's specimens, while in Chevreux's it is still fresh and 

 black. 



Sideplate 1 free of sideplate 2, but not as deep and not quite 

 half its width ; obtusely rounded. Sideplate 2 the deepest of all ; 

 expanded inferiorly ; in Zaddach's specimens and Norman's small 

 one it is deeper than broad, but in the large specimens it is more 

 expanded in proportion to the othei- sideplates, in the largest of all, 

 a female, it is almost twice the width of sideplate 3 ; hind margin 

 straight, front angle produced and I'ounded. Sideplates 3 and 4 

 subequal, deeper than broad, of equal width throughout ; front 

 and hind margins straight ; the 5th has the anterior lobe as wide 

 and as deep as sideplate 4, posterior lobe small ; 6th and 7th 

 small ; 1-5 with a few plumose hairs and setules on the inferior 

 margin. 



Pleoii. — Segment 3 the lai-gest ; the 3rd-6th each with 2 setas, 

 one on either side of the median line, those of the 4th and 5th 

 segments the longest. These setfe are inset submarginally on the 

 posterior margin in the same position as the angles or teeth of 

 the other species. Hind margin of the 2nd segment straight ; 

 that of the 3rd rounded ; inferior margins of 1-3 with plumose 

 sensory hairs, those of the 2nd longer and more numerous ; hind 

 margins 1-3 crenulate, 2-3 crenulations each with a setule inset. 



Antexn^ (fig's. 2 & 3). — Superior Antenna (fig. 2) much longer 

 than the inferior, about half the length of the body : 1st joint of 

 the peduncle stout ; 2nd much more slender and longer than the 

 1st in the large animal, in Zaddach's smaller specimen it was 

 subequal to the 1st in length ; 3rd not quite half the length of 

 the 2nd. Primary Jiagellum : Zaddach gives the number of 

 joints as 12, Norman as 13 ; one of Zaddach's specimens, the 

 smaller of the two, had 11 joints, the other 12; Norman's 

 largest specimen had 14 ; Chevreux's 14, one specimen with 14 

 in one antenna and 15 in the other; the diflerence in number is 

 evidently due to development. The proximal joints are short, 

 the distal ones increasing in length, each, from the 5th or 6th to 

 the second last joint, being furnished with a stalked sensory 

 filament in addition to the small seta3. Accessory fiagelhtm not 

 as long as the 1st joint of the primary. It consists of 1 small 

 joint, which is so constricted near the apex as to give the appear- 

 ance of a minute second joint ; furnished with 3 apical setse, one 

 of great length, and 2 long setae above the constriction. Zaddach 

 completely overlooked this small appendage, which Miiller was 

 the first to note, and indeed it might, as Miiller says, easily 

 escape attention, were it not for the long outstanding apical 

 bi'i sties. 



Inferior Antenna (fig. 3). — The proportions of the last three 

 joints of the peduncle are as given by Zaddach ; 3rd short, nearly 

 twice as broad as the succeeding joints ; 4th the longest ; 5th a 



