258 



ZOOI.OGY OF THE FAR EAST. 











Second peraeopod 



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Palaemon nipponensis, de Haan. 



1890. Palaemon nipponensis, Ortmann, Zool. Jahrb., Sysi., V, p. 715. 

 1902. Bithynis nipponensis, Rathbun, Proc. U.S. Nat. Miis., XXVI, p. 53. 

 1914. Palaemon nipponensis, Balas, Ahhxndl. math.-phys. Klasse K. Bayer. Akad. Wiss., Suppl. 

 Bd. II, Abh. 10, p. 59. 



The synonymy has been dealt with by Ortmann ; more recent references are sup- 

 plied by Balss. 



A number of specimens which show a considerable amount of variation are 

 referred to this species; they were obtained in China and Japan and the largest, 

 which is from the former country, is only 90 mm. in total length. Miss Rathbun has 

 remarked the close relation that exists between P. nipponensis and P. longipes and 

 has noted certain points of distinction, but the use of these characters has not enabled 

 me to separate the collection into two groups. 



In Japanese specimens from 70 to 85 mm. in length the fingers of the second per- 

 aeopods are always shorter than the palm, varying from three quarters to nine tenths 

 of its length; the carpus in specimens with longer fingers is usually more slender, 

 about seven and a half times as long as its distal breadth, while in those with shorter 

 fingers the carpus is generally stouter, hardly more than six times its distal breadth. 

 Distinctions based on these grounds break down entirely when a number of specimens 

 are compared. The upper edge of the rostrum is comparatively straight and in 

 nearly all cases bears 12 or more teeth. I can find no differences in the hairiness or 

 toothing of the fingers of the large chela. 



In young Japanese specimens from 40 to 50 mm. in length the degree of variation 

 in the proportions of the chela of the second legs is even greater than in adults, the 

 fingers being a little longer than, equal to, or only three-quarters the length of the 

 palm. The dorsal teeth on the rostrum are as numerous as in adults, whereas, accord- 

 ing to Balss, there are only 7 or 8 in young P. longipes. 



A Palaemonid from Sagami Bay, about 55 mm. in length, received in exchange 

 from the Munich Museum and determined by Balss as P. longipes, differs in a conspicu- 

 ous manner from aU the specimens in Dr. Annandale's collection. The rostrum is 

 shorter and more strongly arched above, the carapace is thickly covered with minute 



