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



reaching tlae end of the side-plate, the limb in general like that of the preceding pair, 

 with the fifth joint rather shorter. 



Third Perasoj^ods. — Branchial vesicles large, with a long slender appendage arising 

 near the top of the main sac. The first joint longer than broad, with the front margin 

 nearly straight. 



Fourth Perseopods. — First joint long, not much broader above than below. 



Fifth Perseopods. — The first joint large, of even breadth for much of its length, 

 below less abruptly narrowed than in Orchomene musculosus, with which in general this 

 and the other pairs of perseopods closely agree. 



Pleopods. — The two cou^aling spines are very small, each with three lateral retro- 

 verted teeth in addition to the terminal hook. In the first pair the inner ramus carries 

 seven cleft spines, in the third pair six ; the joints of the rami number from sixteen 

 to twenty. 



Uropods. — Peduncles of the third pair much longer than the subequal, slender, 

 stiliform rami, which carry very few and small spines ; peduncles of the second pair 

 longer than the rami ; the outer ramus longer and broader than the inner, with twelve 

 small spines set closely along its upper margin, the inner ramus with three spines on its 

 upper margin at a distance from the apex ; peduncles of the third pair as long as the 

 shorter ramus, the rami broad, lanceolate, reaching much beyond the preceding paii's, 

 the lower rather longer than the upper, ending with a nail, the spines on both few and 

 small, some plumose setse on the margins. 



Telson much longer than its greatest breadth, reaching beyond the peduncles of the 

 third uropods, cleft beyond the middle, slightly dehiscent almost the whole length of the 

 cleft portion, each apex carrying a small spine ; three small sjiines at intervals along 

 each lateral margin. 



Length.- — The specimen, in the position figured, measured, from the front of the head 

 to the Ijack of the third pleon-segment, exclusively therefore of the antennse, three-tenths 

 of an inch. 



ZocaZ%.— Station 323, east of Buenos Ajtcs, February 28, 1876; lat. 35° 39' S., 

 long. 50° 47' W.; depth, 1900 fiithoms ; bottom, blue mud; bottom temperature, 33°'l. 

 One specimen, male. 



Remarks. — The specific name has been given in allusion to the great depth from 

 which the species is reported to have come. The single specimen, a male (as shown by 

 the ventral appendages of the seventh segment of the perseon), was mounted during the 

 voyage. Had this species been taken within any reasonable distance of Orchomene 

 musculosus, the resemblance is so great that one might have been tempted to disregard 

 the points of difi'erence as due to some other cause than difference of species. It might 

 be an accident that has caused one to be reported from the surface, and the other 



