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



The outer plates of the rhipidura are longer than the telson, which is slender, taper- 

 ing to a sharp terminal point, dorsally grooved, and armed on each side with four teeth, 

 of which the posterior is the largest. 



Length, male, 70 mm. (275 in.) ; female, 76 mm. (3 in.). 



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

 Video; depth, 13 fathoms; bottom, mud. 



Thirty-nine specimens ; twelve of which were males and the rest females ; were taken 

 with the trawl, associated with Philonicus miilleri. 



Station 113a, September 2, 1873 ; lat. 3° 47' S., long. 32° 24' 30" W.; off Fernando 

 Noronha, South America ; depth 7 to 25 fathoms ; bottom, volcanic sand and gravel. 

 Only a doubtful fragment of a pleon, which may belong to this species, was here taken. 



This species approaches Aristeus, but it is separated from it by the character of the 

 antennae, the structure and number of the branchial plumes, and also by the form of the 

 mastigobranchial plates. 



The rostrum is long, slender, and horizontal, it is slightly waved, and armed at the 

 base above the orbit with from nine to twelve closely-packed teeth, forming an elevated 

 crest, and further back on the gastric region is one small tooth, from which point to the 

 posterior margin the carapace is smooth, with a slightly elevated bne indicating a 

 suppressed carina. 



The pleon is smooth from the first to the fourth somite, where the suppressed carina 

 reappears and increases to a decided degree on the fifth and sixth somites, on each of 

 which it is produced posteriorly to a small tooth. 



The ophthalrnopod is biarticulate, as in the genus Penseus, and the ophthalmus is 

 ovate. 



The first pair of antennae carries a short and stout stylocerite, and a prosartema on 

 the inner side that does not reach to the extremity of the ophthalrnopod. The peduncle 

 reaches to half the length of the rostrum, and supports two long, slender, subequal flagella. 



The second pair of antennas has the scaphocerite a little shorter than the peduncle of 

 the first pair, and a flagellum that is about once and a half as long as the animal. 



The mandible (d) carries a broad, foliaceous, two-jointed synaphipod, of which the 

 terminal joint tapers to a blunt point. The molar process is continuous with the 

 psalistoma, which is produced anteriorly to a blunt tooth. 



The third pair of siagnopoda (<j) is three-branched. The first branch is squainiform and 

 biarticulate, the inner margin being thickly fringed with cilia. The second represents the 

 basecphysis, and bifurcates into two equally important divisions, of which one is 

 biarticulate and the other squamous ; at or near the base of the latter a foliaceous masti- 

 gobranchial plate originates. 



The first pair of gnathopoda (h) is subpediform, having the three distal joints reflexed. 



