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



another on the outer margin ; the distal extremity supports a long narrow scaphocerite 

 that varies somewhat in form in different species, and the peduncle terminates in a long 

 and slender flagellum. 



The mandibles are deeply inserted within the oral margins, and consist of a narrow 

 molar process, a psalistoma, and a slender three-jointed synaphipod. 



The first pair of siagnopoda is three-branched, and resembles the same appendage in 

 Pandalus. 



The second pair is two-branched and furnished with a large, broad, mastigobranchial 

 plate ; the inner branch is double, short, broad and foliaceous, and the outer short and 

 narrow. The mastigobranchia is produced anteriorly, rounded posteriorly, and bordered 

 with long hairs ; it differs from the same organ in Pandalus in not being prolonged 

 posteriorly. 



The third pair of siagnopoda is five-branched, the first or inner branch is broad, 

 foliaceous, and fringed with cilia ; the second is long, broad and membranous, and of 

 extreme tenuity ; the following branches are long, cylindrical, and tapering. A large 

 mastigobranchial plate, which is divided into an anterior and a posterior portion, is 

 attached to the first or coxal joint. 



The first pair of gnathopoda is short, flat, and formed of six joints ; the first joint is 

 short, and supports a short, broad, mastigobranchial plate with a small podobranchial 

 plume attached ; the second or basisal joint is long, flat on the inner side and rounded 

 on the outer, where it carries a long two-jointed branch, the first joint of which is 

 subcylindrical and the second multiarticulate. The ischium and meros are short, longer 

 on the outer than on the inner margin, and consequently form a curve with each other. 

 The carpos is broader than long, and terminates in a small propodos that corresponds 

 with the carpos, and has the inner or distal margin thickly furred with hairs. 



The second pair of gnathopoda is long and pediform, having the basisal joint furnished 

 with a slender, single-jointed, tapering branch ; the meros is longer than the ischium, 

 the carpos and propodos are subequal, and the dactylos is wanting. This appendage only 

 carries the rudiment of a mastigobranchial plate but no podobranchial plume ; a small 

 arthrobranchia is attached to the membranous articulation. 



The first pair of pereiopoda is long and pediform, scarcely so robust as the second 

 pair of gnathopoda, but much resembling it. It has the dactylos rudimentary, the 

 propodos long and slender, but shorter than the carpos and equally subcylindrical. It 

 has no branch attached to the basis or second joint, and only a small and rudimentary 

 mastigobranchia attached to the coxa, and is without a podobranchial plume. The second 

 pair of pereiopoda is unequal in length, the right being the shorter and more robust ; the 

 right hand is also a little the larger. Both appendages have the carpos long and 

 multiarticulate, that on the left being the more slender and extensively multiarticulate, 

 and carry a rudimentary mastigobranchia but no podobranchial plume. The three 



