14 THE VOYAGE OF H.M.S. CHALLENGER. 



metope ; the second joint is produced at the distal external angle into a strong spine- 

 like process, which is deeply serrate on the outer margin ; within this is implanted a 

 movable appendage, which resembles very much the spine-like process already described ; 

 like it, it is serrate, but not so deeply, on the outer margin ; it articulates with the 

 second joint, and is homologous with the scaphocerite ; the fourth joint is short but longer 

 than the two preceding ; the fifth is very long and cylindrical, supporting at its extremity 

 a slender flagellum less conspicuously nmltiarticulated than the primary flagellum of the 

 first pair. 



The mandibles consist of a pair of strong, externally convex blades, the anterior 

 and upper portions of which articulate with the lower and outer angles of the metope, 

 above which, on the anterior margin, articulates a three-jointed synaphipod, the first 

 joint of which is short and subcylindrical, the second, long and triangular, of which one 

 angle is attached to the extremity of the first joint, another extends upwards and forwards 

 so as to fill the upper portion of the aperture of the mouth, and the third angle supports 

 the third or last joint of the appendage, which is long and tapering, and falls within the 

 mandible; it appears to be hairless, and lies folded between the epistoma and the mandible. 



The first pair of siagnopoda appears ' to consist each of two flat branches — one 

 slender, rigid, and curved, terminating with a fringe of cilia, the other short and 

 membranous, with five or six cilia attached. 



The second pair of siagnopoda is foliaceous and five-branched, four of which are 

 fringed with closely-packed cilia : the fifth is long, slender, flagellum-like, free from cilia, 

 and outside it is a large squamiform plate, copiously fringed with long delicate hairs. 



The third pair of siagnopoda consists of two single-branched, two-jointed appendages. 

 The basal joint is strong, and produced into a lobe internally ; the second or distal joint 

 tapers gradually (the outer margin convex, the inner concave) to the apex. The inner 

 margin is thickly fringed with strong cilia, which increase in length towards the apex. 



The two pairs of gnathopoda are subpediform, and carry each a long secondary ramus 

 (basecphysis) which corresponds in form more with the Macrurous than the Anomurous 

 type of Crustacea. The first pair is small, subpediform, and consists of seven joints ; 

 the second or basisal joint supports a long basecphysis"; the next three succeeding joints 

 are subequal and tolerably robust ; the sixth, or propodos, is short and tapers to the apex 

 from its base ; and the seventh, or dactylos, is unguiculate. The three terminal joints 

 are copiously fringed with long and strong cilia. The basecphysis is comparatively 

 very long, extending considerably beyond that of the primary branch of the gnathopod, 

 which generally lies curved downwards, while the basecphysis extends outwards and 

 upwards. 



The second pair of gnathopoda is much longer than the first, and likewise 



1 I say " appears," because the appendage was broken, the two portions being asunder ; and there is but a solitary 

 specimen in the collection. 



