's RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 105 



1 female collected April 1913 by Mr. E. Jacobson at Telok Beran- 

 dang, Pulu Babi, near Sumatra (2° V N., 96° 40' E.), in the open sea. 



Of the male, which was still unknown and which is 40 mm. long, 

 the rostrum is 1 + 8 dentate and reaches to the far end of 2nd anten- 

 nular article. Fourth abdominal tergum of the male with a shallow 

 tomentose groove on either side and close to the middle line. Left 

 branch of the petasma subacute at the tip, somewhat shorter than the 

 right, by which it is concealed when the petasma is looked at from 

 behind; right branch obtuse at the tip and very convex in the middle of 

 its posterior surface. Female quite typical. 



Penaeopsis assimills n. sp. 



13 males and 10 females collected by Dr. P. Buitendijk off Pulu Weh, 

 near the north point of Sumatra. 



À new species of the Akayebi-group, closely related to Penaeopsis 

 gallensis (Pearson) from Ceylon, but distinguished by the petasma and 

 the thelycum. (J. Pearson, On the Macrura, in: Report on the Pearl 

 Oyster Fisheries of the Gulf of Manaar, 1905, p. 72, PL I, fig. 3). 



Left branch of the petasma reaching much farther beyond the right 

 than in Pen. gallensis, that part which projects beyond the right branch, 

 looks more or less like a sugar-loaf, 3-times as long as broad or thick 

 at base, and measures one-sixth the entire length of the left branch ; this 

 terminal part appears under the microscope smooth and unarmed. The 

 right branch bears at the tip a small prominence turned toward the 

 left and one observes on the anterior side of this branch, distally, a 

 large, regularly rounded lobe. 



A pair of ventral spines between the legs of the 2 nd pair in the fe- 

 male. Between the coxae of the 4th pair one observes, like in Pen. gal- 

 lensis, a transverse crest, acute in the middle and rounded laterally, but 

 between this crest and the posterior wall of the thelycum, which shows 

 also in the middle an acute point, are situated three lobes, one median 

 and two lateral. Median lobe, placed immediately behind the transverse 

 crest, just as long as broad anteriorly; both the anterior and the pos- 

 terior border are emarginate, the antero-lateral angles are subacute and 

 this median lobe seems to be composed of two obtuse ridgès that con- 

 verge backward but posteriorly again diverge. The two lateral lobes, 

 placed between the 5th. pair posterior to the median lobe, consist each 

 of a transverse crest terminating laterally in a subacute tooth ; the two 

 crests are in the middle separated by a smooth interspace. 



