570 ME. W. F. MANCHESTER ON THE . [DeC. 3, 



Dr. Orhnaun (I. c. supra) has given a very brief description of 

 a female, which he considers to be a young form of Heller's species ; 

 and, from the description, T judge him to have been dealing with 

 a form the same as that here under consideration. 



While not denying the possibility of this form being the young 

 of P. idee, I still think there is a strong probability that it is a 

 distinct species, on the ground of the following considerations. 

 There are, in this instance, quite 100 individuals before me, all 

 agreeing in the possession of characters distinct from those of the 

 adult P. idee ; all were collected from the same locality, and there 

 are no specimens showing the size or characters of the adult 

 P. idee ; moreover, in several instances, the females bear 

 numerous AA-ell-developed ova, these females ranging in length 

 from about 25-35 mm. These facts, indeed, are not sufficient to 

 create certainty ; I have at times noticed, for example, the com- 

 paratively small size of ova-bearing females in a species in which 

 a much greater size is the general adult condition, so that physio- 

 logical puberty may not necessarily indicate an arrival at the 

 morphological adult stage. But they do seam to point to a very 

 strong probability that we are dealing here with a distinct speciHc 

 form, and not merely with the young of an allied species. 



XLVI. Genus Pen.eus. 



82. Pen^us SEMisuLCATUs de Haan. 



Penccas semisidcahis, de Haan, Crust. Jap. p. 191, pi. xlvi. tig. 1 

 (1839); Ortmaun, Zool. Jahrb. Syst. v. p. 450 (1891). 



LoQ. Patani, six males and one female. Kelantau, two males. 

 Siugora, one male. 



Length from 7*5 in. to 3*5 in, 



Eostral formula in all but two 7, ; in these two, which are males, 



o 



one has formula ^r the other ^. In the two (smaller) males from 



Kelantau the rostrum is markedly deflected downwards at its 

 point, and does not curve up again as in those from Patani. The 

 ridge of the 6th abdominal segment is transversely notched just 

 behind the middle in one of these males. 



83. Pek^eus velutijS'US Dana. 



Penems velutinus, Dana, U.S. Expl. Exped., .Ci'ust. p. 604, 

 pL xl. fig. 4 (1852); Sp. Bate, 'Challenger' Macrura, p. 253, 

 pL xxxiii. fig. 1 (1888); Ortmann, Zool. Jahrb. Syst. v. p. 452, 

 pi. xxxvi. fig. 6 (1891), 



Loc. Pulau Bidan, Penaug. 



A young male ; length 41-5 mm. 



Q 



Eostral formula -°. To the youth of this individual may perhaps 



be ascribed the t\\x) following points : — Firstly, the crest on the 

 last four segments of the abdomen is very strong and hhuit, that 



