43 i DE. J. G. DE MAN OX CRUSTACEA CHIEFLY 



Nat. Hist. ser. 7, xvi. 1905, p. 526). Each organ consists of a smooth, quite glabrous 

 band, which, arising from the posterior end of the branchiostegite, curves forward, slightly- 

 narrowing distally ; this band carries 18-20 smooth transverse ridges that run parallel 

 with one another ; they are broadest in the middle of the organ and gradually narrow 

 towards both extremities. 



Alcock suggests that JPencBiis alcayehi, Rathb., may prove to be identical with Meta- 

 peiKBus stridulans, W.-Mason, from the east coast of Bengal. I hesitate, however, to 

 identify them, because they belong to a section of this subgenus the sjiecies of which 

 are very closely related and chiefly distinguishable by such slight differences as the 

 shape of the sixth pleoaic segment and the proportion of its length to that of the 

 carapace. Though Alcock's descriptioa of Metap. stridulans agrees very well with 

 these specimens, these characters are not spoken of. I suppose even that Peri, akaijebi 

 is a different species, for the stridulating-organ of Metap. stridulans is usually composed 

 of 5, occasionally of as many as 12, transverse ridges, whereas 18-20 are ol^served in 

 Fen. akayehi. Moreover, the closely related Pen. {Ileta-penceus) accllvis, Rathb., is also 

 furnished with these remarkable organs, and the description of Metap. stridulans 

 agrees very well with this species. 



In Metap. stridulans the " second abdominal tergum is medially carinated in less 

 than its posterior half," and this carina is sulcate ; in Pen. akayehi this carina is hardly 

 grooved, and runs in the iniddle of the tergum. 



Geographical Distribution. — Inland Sea, Bay of Ise, Japan {Kishinouye) : Wakanoura, 

 Kii ; Onomichi, Bingo ; Kawatana ; Hizen, Nagasaki ; Mogi, near Nagasaki, Japan 

 [Batlihun). 



Pen^us (Metapen^us) acclivis, Eathbun. (PI. 33. fig. 55.) 



Parapenaus acclivis, Eatlibun, in Proc. U.S. Nat. Museum, sxvi. 1902, p. 41, figs. 12-14. 



One female from the Inland Sea of Japan, captured at a depth between 5 and 2r> 

 fathoms or more. 



This specimen is 80 mm. long from tip of rostrum to the extremity of the telson. 

 Measured on median line, the carapace appears to be 26'5 mm. long, the rostrum 

 included, and 16 mm. without it ; the sixth segment of the abdomen is 11"3 mm. long 

 just seven-tenths as long as the carapace ; the greatest width of this segment anteriorly 

 is 7'25 mm., whereas it is 5'5 mm. broad posteriorly. The telson is 14-5 ram. long, just 

 twice as long as the greatest width of the sixth segment anteriorly ; the telson, which 

 gradually tapers to the acuminate tip, is armed with one pair of immovable spines, which 

 are preceded by three pairs of strong movable ones ; the immovable spine on either side 

 is barely longer than the anterior movable one, and the two following grow gradually 

 longer, so that the third is three times as long as the anterior spine and slightly extends 

 beyond the immovable. The outer swimmerets hardly reach beyond the extremity of 

 the telson, the inner not at all. 



When the peduncles of the inner antennae are placed immediately below the rostrum, 

 the latter appears to reach a little beyond the end of the second antennular segment, 



