REPOIIT ON THE AMPHIPODA. 811 



PJioxocephalus in accordance with the explanatory derivation which Kroyer supplies at 

 the institution of the genus. 



For the original definition see Note on Kr0yer, 1842 (p. 198). Boeck in 1870 and 

 1876 gives the following : — 



" First Maxillse with the palp one-jointed. 



" Maxillipeds with the palp narrow, the plates small. 



" Third Pereeopods with the first joint dilated behind. 



" Body compressed, deep ; head produced into a broad rostrum, which towards the 

 apex is acuminate or curved. 



" Third Uropods with the inner ramus in the male equalling the length of the outer, 

 in the female much shorter." 



Phoxocephalns bassi, n. sp. [Phoxus bassi, PI. LIV.). 



Head a large triangle, longer than the breadth at the base ; the rostral portion viewed 

 laterally looks like the nib of a quill pen ; it projects as far as the outstretched peduncle 

 of the upper antennae, of which it completely covers the first joint ; the apex is blunt ; 

 the first three segments of the pleon much longer than any of the person-segments ; 

 their postero-lateral angles rounded ; the fourth segment with a dorsal depression ; the 

 fifth very short. 



Uyes large, irregularly quadrate, very dark in the spirit-preserved specimen, with 

 very numerous, small ocelli. 



Upper Antennse. — Peduncles nearly as long as the flagella, first joint longer than the 

 next two united, much thicker than the second, which is longer and thicker than the 

 third ; there are feathered cilia on the first joint, and a group of setaj at the inner apex ; 

 several setae at the outer apex of the second joint have the distal part plumose ; the thii-d 

 joint is thicker but little longer than the first of the flagellum ; the eight joints of the 

 flagellum do not difi"er materially in length but successively decrease in thickness, small 

 calceoli, cylinders, short setae and cilia are among their appendages ; the accessory flagellum 

 of five joints does not quite equal in length the first four of the primary. 



Loiver Antennae. — The first joint somewhat expanded, the gland-cone obscure, third 

 joint broad, not long, distinguished by a furry tuft on the distal jjart of the upper border ; 

 the fourth joint not very much longer, but much broader than the fifth, with partially 

 feathered setae below, and strong flat spines (each with an accessory thread) on the surface 

 and round the distal margin, and on the surface within the upper margin a furry brush 

 of cilia; the fifth joint with a pair of spines about the middle of the upper margin and 

 at its apex, a few small groups of cilia along that margin, and some setae at the apex and 

 on the lower margin near it ; the flagellum is of great tenuity, reaching nearly back to 

 the hinder extremity of the animal ; it consists of thirty-seven joints bearing calceoli on 



