155 



and ciliata. The first species, however, certainly belongs to Eucrate de Haan; longipes is ver)- 

 obscurely known, but according to Stimpson's posthumous treatise ') the front is "deflexed and 

 emaro-inate at the middle" and with a supra-marginal Hne of long hairs, which suggests an 

 affinity to Litocheira Kinahan; sculpta is according to Stimpson's figure ") too much sculptured 

 to belono- to Pilunmoplax and the front is Hkewise deflexed^); finally ciliata is doubtless a 

 species of Litocheira. 



The name should, then, become a synonym, parti)- of Ejicrate, partly of Litocheira, 

 but Miers afterwards included into Pilumnoplax two species, which certainly warrant the 

 constituting of a new genus and, though strictly speaking the name given by Stimpson is not 

 admissible, I have retained it here. We must in this case adhere to Alcock's definition *) of 

 the genus, and particularly exclude from it those species with the front turned strongly down 

 and bilobed; in genuine Piluninoplax the front is, on the contrary, feebly deflexed, 

 in a line with the g ener al longitudinal curve of the carapace, overhanging 

 the anten nul ae, and with the anterior margin perfectly straight and usually 

 entire; the carapace is flattened from side to side and hairless; the ambulatory legs are slender. 



Tl-ie species of the genus thus restricted are all inhabitants, as far as is known, of the 

 deeper parts of the ocean bottom, save P. vestita (de Haan), which seems to live in shallow 

 water. This species deviates also in its outer aspect from the other species, for the carapace, 

 the legs and especially the chelae are very hairy, the front does not overhang the antennules, 

 and the legs are stout and short; yet, following Miers and Ortmann, I have let it retain its 

 place in the present genus. On the other hand I have serious doubts about the true systematic 

 place of P. aca}ithoiiicriis Rathbun °), found at only 30 fathoms near the Amirante Islands in 

 the Western Indian Ocean. This species has the front nearly half as broad as the carapace, 

 with the anterior edge sinuous, emarginated in the middle and near each lateral angle, the 

 chelipeds and ambulatory legs are profusely spiny, stout and bulky. 



I thus admit only the following species, one of which has been brought home by the "Siboga" : 



P. vestita (de Haan) 

 P. heterocheir (Studer) 

 P. abyssicola Miers 

 P. glaberrima Ortmann 

 P. americana Rathbun 

 P. cooki Rathbun. 



Key to the species : 

 I . Carapace much hairy, with two widely separated, little prominent 

 teeth behind each external orbital an^le. Chelae with a long 

 fur on proximal and upper part of outer surface. Ambulatory 



1) Smithson. Inst., Miscell. Coll., v. 49, 1907, p. 91. 



2) Ibid., p. 91, pi. II, f. 3. 



3) I shall vefer to this species later on, as the "Siboga" caught a species neaily related tü it. 



4) "Investigator" Deep Sea Brachyura, 1899, p. 74; Journ. As. Sec. Bengal, v. 69, pit 2, 1900, p. 311. 



5) Transact. Linn. Soc. London (2), v. 14, 191 1, p. 237, pi. 18, f. 3. 



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