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



anteriorly-directed tooth : the third, fourth, and fifth somites are similar, except that 

 posteriorly they become narrower, carry a smaller coxal plate, and have the dorsal 

 median tooth diminishing gradually to a cusp : the telson is long and tapering, armed 

 on the median line near the base with a small posteriorly-directed cusp. 



The ophthalmopod is situated in a wedge-shaped cleft, which is narrower at the base 

 than at the anterior margin, where it is armed with a sharp and rigid tooth, and projects 

 downwards and outwards, being compressed between the upper surface of the second 

 pair of antennas and the extension of the latero-anterior angle of the carapace. 



The first pair of antennas has the anterior extremity of the inner squamiform process 

 produced to a sharp tooth, and armed along the inner margin, which is curved upwards, 

 with two or three small teeth and a few* hairs, and carries one sharp tooth on the outer 

 anterior angle above the auditory slit ; the two succeeding joints of the peduncle are 

 short, not reaching so far as the apex of the inner tooth of the first joint ; the outer 

 flagellum is about one-fourth the length of the inner, and more slender. 



The second pair of antennas has the phymacerite long, and compressed closely against 

 the inferior surface of the first joint of the first pair of antennas ; the extremity of the 

 peduncle reaches beyond that of the first pair ; the flagellum is as long as the inner 

 branch of the first pair ; and the scaphocerite, which is long, narrow, and pointed, does not 

 extend beyond the extremity of the last joint of the peduncle, although so figured in 

 the plate (fig. lc. c). The surface of the peduncle is covered with hairs, and so is the 

 margin of the scaphocerite. 



I have not disturbed the oral appendages, as the specimen is unique, and the general 

 similarity of the external parts is suggestive of no great variation in hidden structure. 



The second pair of gnathopoda carries a small and slender mastigobranchia, but 

 has no podobranchial plume attached. It corresponds closely with the same organ in 

 Pentacheles Iwvis. 



The first pair of pereiopoda is long and slender. The meros is smooth upon the outer 

 margin, except that it is armed with a single tooth on the distal or carpal extremity ; 

 the inner margin is furnished with a row of small teeth, the three or four nearer the 

 ischium being sharp and well defined ; the carpos is long, slender, and smooth, except 

 for one small tooth at the external distal angle ; the propodos is fringed with fine 

 teeth on the external margin and a few rudimentary ones on the inner ; the dactylos 

 is parallel with the pollex, excepting that both are curved laterally inwards and overlap 

 each other when closed. The coxa carries a long and broad mastigobranchia, with a 

 podobranchial plume attached to it. At the articulation are two arthrobranchias, a large 

 posterior and a small anterior, but no pleurobranchia. 



The second pair of pereiopoda is tolerably robust. It is short and carries two 

 arthrobranchias, a podobranchia, and a mastigobranchia. 



The two following pairs are more slender, and possess a similar branchial arrangement. 



