'4 



f I. Benthesicyvius Iiivestigatoris A. And. 



A. Alcock and A. R. S. Anderson, Ann. Mag. Nat. Hist. Ser. 7, Vol. Ill, April 1899, p. 282. 

 A. Alcock, Indian Deep-Sea Crustacea, Decapoda Macrura and Anomala, 1901, p. 44. 



Illustrations of the Zoology of the Investigator, Crustacea, PI. XLI, Fig. 2, 1899. 



M. J. Rathbun, Bull. U. S. Fish Comm. for 1903, Wash. 1906, p. 906. 



Stat. 161. August 17. 1° io'.5 S., 130° 9' E. Halmahera Sea. 798 m. Muddy sand, i female. 

 Stat. 178. September 2. 2°40'S., I28°37'.5 E. Ceram Sea. 835 m. Blue mud. i male and i female. 



These specimens agree very well with Alcock's description and figure, except as regards 

 the thelycum, while the chelate legs appear a little more slender than in the quoted figure 

 of the "Illustrations". According to the original description the thelycum consists "of a tubercle 

 between the 3''*' pair of legs followed by two transverse bands lying respectively between the 

 4'^ and 5'"^ pairs of legs, the first of these bands being sinuously notched anteriorly, the 

 second being simply notched posteriorly". In the two females captured by the "Siboga", one 

 observes between the coxae of the 3''<i legs a triangular tubercle, rounded posteriorly and which 

 is followed by a single plate, somewhat longer than broad, lying between the legs of 

 the 4''' and s'"^ pairs. Anteriorly this plate is emarginate, while the anterior margin projects a 

 little in the middle ; the rounded posterior margin is simply notched in the middle and at 

 either side the upper surface is hollowed out or concave, so that this organ appears faintly 

 though obtusely carinate in the mid-line. The coxae of the 4''^ legs show at the inner side a 

 semicircular, compressed process, fringed with hairs ; these processes partly cover the concave 

 lateral sides of the plate. 



In the female from Stat. 161 the carapace with the rostrum is 21,5 mm. long, so that 

 this specimen has almost attained the length of 24 mm. indicated by Alcock, but, according 

 to Miss Rathbun, carapace and rostrum attain a length of 32,2 mm.; the two other specimens 

 are of a smaller size, the carapace with the rostrum measuring 18 mm. in the male and 15 mm. 

 in the lemale. In the male the two branches of the petasma are not yet united. 



In these specimens the rather sharp post-rostral crest is produced as far as the deep 

 cervical groove, i. e. the anterior of the two grooves, and po.sterior to the cervical groove the 

 carapace is rounded. The post-cervical groove extends almost to the upper border of the 

 carapace and is less deep than the cervical. The "very small rudiment of a movable spine, 

 behind the posterior tooth of the rostrum" described by Miss Rathbun (1. c.) seems to have 

 been present also in these specimens, but to be broken off. No hepatic spine. The three anterior 

 abdominal somites are rounded, the 4'^^ bears a distinct carina, that reaches from the posterior 

 extremity to just beyond the middle, but does not terminate posteriorly in a tooth. The rather 

 sharp carinae of the 5* and 6'^^ somites terminate in a tooth, the carina of the 5'!^ extends 

 along the two posterior thirds of the somite. The telson, a little shorter than the 6"^ somite, 

 is much shorter than the inner lamella of the caudal fan; the strongly tapering telson is 

 rounded on the anterior and slightly flattened on the posterior half; there are probably three 

 pairs of small spinules near the tip. 



Eye-peduncles longer than the rostrum, flattened above ; tubercle on the inner margin 

 small and acute. In the largest specimen, the female from Stat. 161, the cornea has a rather 



14 



