In the Leiden Museum at present still only one type specimen of de Haan's Peneus 

 ensis is preserved (W. de Haax, Fauna Jap. Crust, p. 192, PI. 46, fig. 2). Dr. R. Horst of 

 this Museum sent me with his usual courtesy upon my request the following information 

 about this type specimen. In P. ensis an obtuse, though quite conspicuous crest runs from 

 the hepatic spine to the posterior border of the carapace (a posteriore (spina) costa obtusa 

 ad marginem posticum producta) ; the peraeopods of the i^' pair are bispinose , like in 

 Pen. mtertnedia and the new variety, the spine of the ischium is, however, much smaller than 

 that at the base; there is a quite distinct flattened keel on the 3"' abdominal tergum and 

 the \^^ to e'*' are sharply carinated, while one observes moreover a crest on the posterior half 

 of the 2°^; of the three lateral spinules of the telson the two posterior are rather long, like 

 in the typical intermedia, the anterior only half as long; in P. ensis, finally, the rostrum is 

 slightly directed upward. It is thus evident that P. ensis is a different species, chiefly distin- 

 guished by the obtuse crest, which from the hepatic spine runs backward, and by the stronger 

 carination of the abdomen. 



5. Penaeopsis sp. PI. I, fig. 4 — \b. 



Stat. 166. August 22. 2°28'.5S., i3i°3'.3E. Midway between Ceram and New Guinea. iiSm. 

 Bottom hard, coarse sand. 5 very young specimens. 



I do not succeed in determining these specimens, because they are too young, so that 

 neither petasma nor thelycum are developed. It is a species of the Akayebi-group and most 

 closely related to or perhaps identical with Pen. dardaius (de Haan) = Pen. Akayebi (Rathb.) 

 from Japan. The largest specimen measures about 27 mm., the others are still younger. In all 

 the specimens (Fig. 4) the rostrum, which is obliquely turned upward, reaches to the far end of basal 

 antennular article, but we know that in such young individuals it is much shorter than in the 

 adult; the rostrum is slender, tapering, straight and in all the specimens i 4- 6-dentate, the 6 

 teeth are equidistant, reach to the tip and from the 3"' decrease in size. Epigastric tooth a 

 little smaller than the i^^ rostral tooth. First abdominal tereum rounded, the 2°<i shows in the 

 largest specimen and in another, but not yet in the rest, a trace of a low carina on the 

 anterior half, the 3'''^ and following terga are conspicuously carinated, the carina of the 3''^ 

 .slightly broader than those of the following. Si.xth somite (Fig. 4(7) much elongate, in the largest 

 specimen it is 4,6 mm. long, as long as the carapace from the orbital to the posterior margin, 

 and 2'/^ -times as long as broad pro.ximally; it is more than twice as long as the 5''' 

 and a little longer than the telson which is armed with one fixed and three movable spines 

 at either side, while at least on the posterior half (Fig. i^b) much smaller spinules are implanted on the 

 lateral margins between the three large spines and in front of them. In the youngest specimen 

 the telson, 3 mm. long and i mm. broad proximally, appears even 3-times as long as broad, 

 and the telson is here 2,56 mm. long. Telson much shorter than the uropods. We may there- 

 fore conclude that in adult specimens the 6"^ somite will be twice as long as broad, which fact in 

 Peii. barbatus (de Haan) seems to be indeed the case, according to the figure 2 on Plate VI 

 of Kishinouve's paper of 1900, representing the Pen. veluiifins of this author, which is identical 

 with J^en. barbatus and Pen. Akayebi {M. J. Rathbun, in : Proc. U. S. Nat. Mus. XXVI, 1902, p. 39). 



