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



moderate lengtli, with the joints finely tubercular above ; the meri are dilated, and their 

 anterior margins are pubescent ; the dactyli are short and strongly curved, with their 

 posterior margins entire. 



The eyes are freely movable, with the cornese subglobose and terminal in position ; the 

 peduncle is slightly elongated, but not prolonged into a spine. The antennal flagellum 

 is not equal in length to the carapace. The ischium and merus of the external maxilli- 

 pedes are faintly granular externally ; the outer margin of the former is prolonged 

 distally into an acute spine, while the inner margin of the latter is irregularly dentate, 

 and a curved acute spine is placed at the distal end and outer border of the same joint. 



The second and third abdominal segments are each provided with a prominent 

 median tubercular elevation, the surface of which is roughened, and scattered tubercles 

 of small size are present towards the lateral margins of the same segments. The 

 posterior segments are perfectly smooth. 



Several of the distinctive features of this species are peculiar, as for instance the 

 flattened carapace, the bidentate rostrum, the short curved ambulatory dactyli, and the 

 median abdominal tubercles ; but they are not, in my opinion, suflicient to separate it 

 from the genus Elasmonotus. Females are apparently slightly larger than males, their 

 rostrum is more strongly developed, and their chelipedes are shorter. 



Breadth of carapace (of an adult male) 8 mm., length of body (including rostrum) 

 24 mm., of carapace (including rostrum) 13 mm., of chelipede 31 mm., of first 

 ambulatory leg 18 mm. The ova measure about 1 mm. in diameter. The body of the 

 largest female measures 29 mm. in length. 



Habitat} — Station 311, ofl' Port Churruca, Patagonia; depth, 245 fathoms; bottom, 

 blue mud. Upwards of a dozen specimens, the majority of which are females with ova. 



Elasmonotus IsBvigatus, Henderson (PL XVIII. fig. 3). 



Galathopsis Ixvigata, Henderson, Ann. and Mag. Nat. Hist., ser. 5, vol. xvi. p. 417, 1885. 

 Characters. — The carapace is comparatively smooth, only a few very slight rugosities 

 being present on the gastric, cardiac, and posterior branchial regions, while a slight 

 pubescence occurs on the upper surface of the rostrum, and towards the lateral margins 

 in front. The gastric area is strongly convex, and rises considerably above the level of 

 the rostrum, but there is no sharply defined ridge between the two ; the cardiac area is 

 crossed by a moderately deep transverse groove. The rostrum is flattened and depressed 

 on the whole, though the acute apex is slightly upturned ; its lateral margins are thin 

 and entire. The lateral margin of the carapace is armed with two small acute teeth, one 

 placed at the commencement of the border, the other immediately behind the cervical 

 groove, and a single acute triangular tooth of slightly larger size occurs on the antero- 



' This species is erroneously recorded from Station No. 107 in my preliminary account, an error due to a mistake 

 in the labelling of one of the specimens. 



