160 THE VOYAGE OF H.M.S. CHALLENGEE. 



Elasmonotus latifrons, Henderson (PI. XIX. fig. 1). 



Elasmonotus latifrons, Henderson, Ann. and Mag. Nat. Hist., ser. 5, vol. xvi. p. 416, 1885. 



Cliaracters. — The carapace is strongly arched from side to side, and covered every- 

 where with tubercular granules, many of which are compound. The gastric area is 

 convex, and provided in front with two slightly-rounded elevations which overhang 

 the base of the rostrum ; the cardiac area is circumscribed, and a moderately deep 

 transverse groove separates a posterior triangular portion from two lozenge-shaped 

 portions in front. The rostrum is broad, flattened, and horizontal, with the apex acute, 

 and a notch occurs on either side of the base, into which the eye-stalk fits ; the upper 

 surface is finely granular and traversed by a faint median carina ; the lower surface is 

 smooth, and faintly earinated towards the apex, while the lateral margins are finely 

 serrated, especially towards the apex. The lateral margin of the carapace is notched by 

 the two divisions of the cervical groove, and a slight projection is present on the orbital 

 border behind the antennal peduncle ; the posterior margin is raised and granular. 



The chelipedes are short and stout, with the joints granulated ; a spine is present at 

 the distal end of the merus on both its inner and outer surfaces, and a third exists on 

 the inner margin near the distal end of the carpus. The propodus is rather finely 

 granulated, but devoid of spines ; the fingers arc scarcely equal in length to the palm, 

 and their surface is pubescent, while each is deeply excavated on its inner aspect towards 

 the apex, and the apical margin is finely dentate externally. The ambulatory limbs are 

 short and robust, with the joints granulated, and a few short blunt spines are present on 

 the anterior margins of the meri, carpi, and propodi ; the dactyli are short, and each ends 

 in a curved, horny claw, while a few short teeth occur on their posterior margins. 



The eyes are of small size, but slightly movable, and partially concealed by the sides 

 of the rostrum ; the peduncle is granulated, and prolonged a short distance beyond the 

 rudimentary cornea in the form of a blunt spine. The basal joint of the antennular 

 peduncle is granulated. The merus of the external maxillipedes has its inner margin 

 armed with minute teeth, which are somewhat closely arranged on the proximal half. 



The second, third, and fourth abdominal segments are transversely sulcate, with a 

 granulated carina on either side of the groove ,* the lateral margins are granulated, as is 

 also the whole surface of the posterior segments. 



This species is characterised by the form of its rostrum, and the presence of tubercular 

 granulations on most parts of the body. 



Breadth of carapace (of an adult male) 11 mm., length of body (including rostrum) 

 34 mm., of carapace (including rostrum) 17 '5 mm., of chelipede 22 mm., of first 

 ambulatory leg 20 mm. 



Hahitat. — Station .218, between Papua and the Admiralty Islands; depth, 1070 

 fathoms ; bottom, blue mud. A single specimen. 



