240 

 I. Hexapus sexpcs (Fabricius). PI. 17, Fig. i. 



Literature: Stebbing, Ann. S. Afr. Mus., v. 6, 1910, p. 315 '). 



Stat. 37. Sailus Ketjil, Paternoster Islands. Depth up to 27 m. i 9- 

 Stat. 258. Tual, Kei Islands. Depth 22 m. 2 cf- 



The descriptions and figures of A. Milne-Edwards"), de Man ■') and Stebbing*), especially 

 those of the two latter authors, are so complete that a thorough description may be dispensed 

 with. In comparing the somewhat different appearances of the animals figured we are led to 

 the conclusion, that in young individuals (length of carapace 3 mm.) the breadth of the carapace 

 is twice its length, the surface pubescent throughout, and the postero-lateral margins strongly 

 divergent backward, but that with advancing age the- carapace becomes proportionately narrower, 

 the postero-lateral margins assume a subparallel coiirse, though developing a strongly convex 

 bulge near the posterior angles, and the pubescence is gradually lost. The number of- 

 oblique ridges on the pterygostomian regions seems to vary individually, independent of age '). 

 Miss Rathbun °), in describing her Laiubdophalhis anfractus, doubts whether the speci- 

 mens of DE Haan, A. Milne-Edwards and de Man are really identical. Besides the "Siboga" 

 specimens I have also examined de Haan's original individual, which is still preserved in the 

 Leiden Museum, and after close inspection I find them all wholly identical. Neither do 

 I hesitate to maintain the correctness of the determinations both of Milne-Edwards and of de Man. 



The following particulars will be of some use : 



i'^ The regions on the carapace are usually not perceptible ■, the postero-lateral margins exhibit, 



save perhaps in very small individuals, a somewhat flattened, prominent lobe near their 



distal ends. 



2" The front is nearly vertically deflexed, about one-fifth of the width of the carapace and 



truncate ; the eyes are globular, with normal cornea, but with the pigment brown and scanty ; 



the eye-stalks are not firmly fixed ; there is a supra-ciliary groove along the supra-orbital margin. 



3" The antennulae are transverse; an epistome is distinct, and the lateral walls of the buccal 



cavity diverge backward. External maxillipeds gaping, the gap being for a large part 



filled up by the palpi; when deprived of the thick coating of hairs, merus and ischium 



have a characteristic shape (fig. i a) and the fact that they are incorrectly represented by 



de Haan ') induces me to figure them anew, also in order to compare my statements with 



Stebbing's figure : ischium narrow, not longer than merus, with a large widening at the 



inner distal angle^); merus oblong, rounded, with the palp inserted at the tip; carpus thick 



and short, presenting a strong tuft of feathered hairs ; pro2:)odus in Stebbing's figure longer and 



i) Stebiiing has overlooked Zehntner's record of the species (Rev. suisse zool., t. 2, 1894, p. 159) and also that of A. Milne- 

 Edwards (see note 2). 



2) Nouv. Arch. Mus. Paris, t. 9, 1873, p. 253, pi. 12, f. i. 



3) Arch. Naturgesch., Jahrg. 53. i., 1888, p. 322, pi. 13, f. 3. 



4) L. c, p. 315, pi. 41. 



5) It must be noted, however, that Zehntner in a very large individual from Amboyna (length of carapace 15 mm., breadth 

 23.5 mm.) States the complete absence of these oblique ridges. 



6) K. Dansk. Vid. Selsk. Skr., 7. Raekke, Afd. 5, n" 4, 1910, p. 349. 



7) Faun. Japon., Crust., 1835, pi. D. 



8) Ischium, according to Stebping's figure, longer than merus, with the lateral margins parallel over their greater part. 



92 



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