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



The pleon is dorsally carinated from the third somite to the extremity of the 

 sixth, which is posteriorly produced to a sharp tooth ; aud the telson is dorsally 

 grooved in the median line, and armed on each side with one strong tooth and a fringe 

 of hairs. 



The first pair of antennae is nearly as long as the entire animal. The second pair is 

 about four times as long ; they are respectively shorter in the male than in the female. 



Length — male, 76 mm. (3 in.) ; female, 152 mm. (6 in.). 



Habitat— Station 321, February 25, 1876; hit. 35° 2' S., long. 55° 15' W.; off 

 Monte Video; depth, 13 fathoms; bottom, mud. Thirty specimens. Five males and 

 twenty-five females. Trawled. 



The rostrum, measured from the frontal margin of the orbit to the apex, is less than 

 half the length of the carapace ; it is produced horizontally and slightly crested over the 

 orbit. It is armed with eight teeth in the largest female specimen, the posterior of 

 which is situated slightly anterior to the cervical furrow, and they are continued, with a 

 little tuft of cilia between each, to within a short distance of the apex, the largest teeth 

 being over the orbit. The under margin is smooth, curved slightly upwards to the 

 extremity, terminates in a point in the plane of the upper margin, and is fringed with 

 hairs. The pleon is smooth except for a dorsal carina, which is slightly indicated on the 

 first three somites, but is more conspicuous on the posterior three somites. The first 

 somite laterally overlaps the posterior margin of the carapace, and posteriorly overlaps 

 the anterior margin of the second ; the second posteriorly overlaps the anterior margin of 

 the third, and the same relation occurs in all the succeeding somites. 



The ophthalmopod is large and biarticulate ; the ophthalmus is oval and wider than 

 its stalk. 



The first pair of antennae has the first joint of the peduncle armed on the outer 

 side with a sharp-pointed stylocerite, and furnished on the inner side with a, thickly 

 ciliated prosartema that reaches to the extremity of the rostrum, between which and the 

 stylocerite the eye, when at rest, is lodged. The second and the third joints are short 

 and terminate in two subequal flagella, of which the upper is rather the longer. 



The second pair of antennae carries a broad scaphocerite that reaches considerably 

 beyond the extremity of the rostrum, and even beyond the distal extremity of the third 

 joint of the peduncle of the first pair, and terminates in a long and slender flagcllum, 

 which in one, the largest female specimen, was about four times the length of the 

 animal. The mandible carries a large, ovate, foliaceous synaphipod, the first joint of 

 which is broader than the second, which tapers to a point, and the entire surface is 

 furred with short hairs. The psalisiform margin is blunt, smooth, and connected with 

 the molar tubercle, which is smooth and strong. 



The first pair of gnathopoda is short, subpediform, six-jointed, with the two ultimate 



