REPORT ON THE CRUSTACEA MA CRURA. 317 



Aristeus rostridentatus, Spence Bate (PI. LI.). 



Aristeus rostridentatus, Sp. B., Joe. eit, p. 189. 



Carapace smooth. Kostrum markedly elevated anteriorly, as long as the carapace. 

 Dorsal surface crested above the frontal region, serrate with distantly placed teeth from 

 the posterior portion of the crest to the extremity of the rostrum. Lower margin 

 smooth. Frontal margin of the carapace armed with a first and a second antennal tooth ; 

 a sharp tooth on the hepatic region. 



The pleon is slightly compressed posterior to the third somite. The third, fourth, 

 fifth, and sixth somites are slightly carinated, and have the posterior margin produced 

 to a small tooth in the median dorsal line. The telson is long, and tapers to a styli- 

 form point ; the dorsal surface is slightly grooved ; the sides are depressed, and the 

 margins are fringed with a thick row of hairs and four small spines. 



The ophthalmopod is short and small, the ophthalmus large and round. The first pair 

 of antennae has the peduncle half the length of the rostrum; the first joint is a little longer 

 than the ophthalmopod and supports a stylocerite that reaches beyond the eye, but does 

 not extend to the extremity of the first joint. The second joint is rather shorter 

 than the first ; it is cylindrical and hirsute. The third joint is nearly as long as the 

 first, and carries the smaller flagellum near the base and the longer at the apex ; the 

 former is not longer than the joint that supports it, whereas the latter is longer than 

 the animal. 



The second pan of antenna? is about four times the length of the animal, and has a 

 scaphocerite extending as far as the extremity of the peduncle of the first pair. 



The first pair of gnathopoda is short, and carries an ecphj^sis much longer than itself. 



The second is long, and carries an ecphysis that is about one-third its length. 



The pereiopoda approximate to each other ventrally, and a small vertical plate 

 projects between the coxas of the fourth pair, which are hirsute. A prominent and sharp 

 tooth stands between the pleopoda, which are of only generic value. 



Length, largest about 131 mm. (5'25 in.), smallest 38 mm. (T5 in.) 



Habitat— Station 173, July 24, 1874 ; lat. 19° 9' 35" S., long 179° 41' 50" E.; near 

 the Fiji Islands; depth, 315 fathoms; bottom, coral mud. Three specimens; females. 

 Dredged. 



This species bears a general resemblance to Aristeus armatus, and might on a hasty 

 examination be taken for a variety of that species, but a detailed examination shows that 

 there are some very important differences that separate them widely. The rostrum, 

 continuing the anterior slope, of the carapace, is first depressed, and then it somewhat 

 suddenly ascends. It carries on the dorsal surface numerous distantly situated small teeth. 

 These, from their number and position, furnish a ready means of diagnosis, but it is 



