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



The second pair of gnathopoda is long and robust, reaching beyond the extremity of 

 the peduncle of the first pair of antennae, and terminating in a small, compressed, curved 

 dactylos; it is thickly fringed with hairs and carries a long, slender basecphysis; like the 

 pereiopoda it has no tooth at the base. 



The first pair of pereiopoda is short and moderately strong, and each succeeding pair 

 increases in length and becomes more slender, so that the last two pairs are exceedingly 

 long and slender. 



On the ventral surface of the pereion there is an orange-coloured, discoid mass 

 between the coxae of the fourth pair of pereiopoda, immediately posterior to the extremity 

 of the projecting processes on the third pair of pereiopoda that carry the oviducts, while 

 the surface between, and posterior to the last pair of pereiopoda, is smooth and even as far 

 as the median line between the first pair of pleopoda, where there arises a large, laterally 

 compressed, anteriorly pointed and posteriorly curved tooth. 



The first pair of pleopoda is long, slender, and single-branched; a rudimentary mem- 

 branous petasma exists on the inner side of the basisal joint. All the other pleopoda 

 are biramose, the outer or posterior branch being long, and the inner one short; they 

 gradually decrease in length but gain in equality posteriorly. The posterior pair forms 

 the branches of the rhipidura. The outer is much longer than the inner, and the inner is 

 much longer than the telson, and is leaf-like and partly strengthened by a rib in the 

 median line ; the outer is ovate, and strengthened by a rib that meets the outer margin 

 considerably short of the distal extremity. 



The branchiae are of generic value, but differ a little in the relative proportions of the 

 several plumes. The pleurobranchiae are small but increase in size posteriorly, yet the last, 

 although the longest, is not a large or important appendage. The arthrobranchiae are large 

 and overlap each other, except in the last pair, where there is no podobranchial plume, 

 whereas a long and well-developed podobranchial plume is attached to every mastigobranchia 

 except that which belongs to the penultimate pair of pereiopoda. The mastigobranchiae 

 are all thick and fleshy, and have the surface marked with numerous straggling hairs. 



Thus there are seven pleurobranchiae, twelve arthrobranchiae, five podobranchise, and 

 six mastigobranchiae, the tendency of which is to increase in size posteriorly. 



About fifty miles south of Japan, just where the water rapidly deepens from a 

 hundred fathoms to between three and four thousand, four specimens were taken ; 

 three of them were males, about half the size of the female, and had the eyes in one 

 instance dark brown all over, while in the others the brown pigment affected only the 

 base of the eye, but to a greater extent than in the specimen described. The bottom was 

 green mud, and the temperature was 2°"1 higher than at Station 184. At the eastern 

 entrance of Torres Strait, it was taken with the trawl in a deep ravine between the 

 hundred fathom areas that surround the New Guinea and Australian coasts, being the 

 deepest water in which this species has been taken. 



