3Q 



on carapace (which is covered by a short fur) absent .... R. chuni Doflein (=R. 



dentata Mac Gilchrist) 

 Sides of carapace angular, not toothed, but everywhere finely serrated. 

 Supra-orbital tooth absent. Two transverse sutures on carapace, 

 which is almost hairless R. plumosa n. sp. 



i. Rctropluma plumosa n. sp. PI. 2, Fig. 1. 



Stat. 254. 5°4o'S., i32 2Ó'E. Near Kei Islands. Depth 310 metres. Fine, grey mud. 1 (ƒ. 



In some respects this species agrees either with the type species óf Alcock or with the 

 species of Doflein and. of Mac Gilchrist. With R. notopus it shares the angular shape of the 

 carapace (though in the new species there is one additional angulation behind the external orbital 

 angle), the two transverse sutures, and the faint development or absence of a supra-orbital 

 tooth; on the other hand the "Siboga" species agrees with R. chuni and dentata in the shape 

 of the rostrum, in the granulation of the meropodites of the walking legs (as in R. dentata), 

 in the 4 longitudinal sharp ridges on the dactyli (as in Tv. chuni) and in the shape of the 

 abdomen of the c? (as in R. dentata), but as the descriptions of the different species either in 

 this or in another point are not quite complete, several characters may be called generic rather 

 than specific. 



The carapace is wholly flattened, very slightly granular and naked, except for some 

 short hairs at the margins. Two transverse sutures divide the surface into three parts; the 

 anterior of which slopes obliquely-forward and terminates in the median line into a small, slender, 

 somewhat deflexed rostrum, tapering to tip, reaching as far as the basal joints of the antennulae 

 and beyond the line connecting the external orbital angles; the posterior part of the carapace 

 is likewise somewhat, though less, oblique, and the convex posterior margin passes with a 

 distinct angle into the subparallel lateral margins. The distance between the external orbital 

 angle is 5 / 8 of the whole breadth of the carapace, and the supra-orbital border is long, concave, 

 and without any tracé of a tooth, but showing a re-entering angle at the place where such a 

 tooth exists in R. chuni and dentata l ). Parting from this point, the superior orbital border 

 passes obliquely forward to the rectangular external orbital angle, which is finely crenulate, 

 the crenulations being directed outward at the anterior and forward at the outer border; the 

 outer border (the antero-lateral border of the carapace) slopes obliquely-outward towards the 

 next angulation (anterior lateral tooth), which is little prominent, finely crenulate, and connected 

 with the angulation of the other side by the anterior, somewhat convex, transverse suture of 

 the carapace. Behind this angulation the lateral margins of the carapace are subparallel or 

 slightly converging posteriorly, but there is a second indentation (posterior lateral tooth) about 

 at the level of the bases of the chelipeds. Behind these posterior teeth, and a little way 



1) There is some confusion regarding the external orbital angle, among the authors. Doflein expressly states that he regards 

 the supra-orbital tooth, to which the eye extends, as the real orbital angle and he consequently calls the next tooth, which is on the same 

 level with this supra-orbital one, the antero-lateral tooth; hence his statement that the borders of the carapace are armed with three pairs 

 of teeth. I have foliowed Alcock in regardiog this latter tooth as the real orbital angle, as to this point the incomplete orbito-anten- 

 nulary fossa is continued outward. 



3° 



