MARINE AMHIimns FROM PERU. 



By Alfred (). Walker, 



Of Maidstone, Kent, England. 



The Amphipoda from Chincha Islands arc all of one species to 

 which I have given the name Stenothoe assimilis Chcvreiix." with 

 which species it agrees except in having more spines on the telson and 

 third uropods. From S. <j<ilh nsis Walker'' it differs in the last joinl of 

 the third uropods of the male, which in my species i^ upturned, ser- 

 rate and blunt, while in the Peruvian specimens and in S. assimilis it 

 is straight, smooth, and sharply pointed. 



Both these species are so closely allied to S. valuta Dana, 1852, 

 that but for the fact that he has figured the third perseopods with a 

 wide basal joint instead of the narrow one of the above two species, 

 they might both be referred to it, uotwithstanding the trifling differ- 

 ence in the third uropods. I have a strong suspicion thai if Dana's 

 type-specimen could be discovered, il would be found that he had 

 overlooked the difference in the form of the joints. S. assimilis would 

 then be a synonym of S. valida. c 



STENOTHOE ASSIMILIS Chevreux. 



Abundanl in hydroid colonies on bol toms of " lanehas " i lighters used in embarking 

 guano). 



DESCRIPTION OF THE SPECIES BY CHEVREUX (TRANSLATION). 



Male. Body rather Btout, 5 mm. long, in the position figured. Head without 

 rostrum; lateral lobes not prominent, rounded. Coxal plates of second pair subtrian- 

 gular, anterior margin very convex, inferior margin concave. Coxal plates of third 

 pair larger than those of Eourth pair. Posterior angles of epimeral plates of lasl seg- 

 ment of metasome a little produced backward, hardly acute 



Eyes of medium size, round, containing a very la rue uumber of ocelli. 



Superior antennae equal in length to sum of head and first four Begmentsof meso- 

 some; firsl article of peduncle nearly as long as head, much longer than second 

 article; third article \erv short, not quite bo long as firsl article of flagellum; the 

 latter much longer than peduncle and composed of fifteen articles. The inferior 

 antenna' surpass somewhat the superior: flagellum much shorter than lasl two article 

 of peduncle and containing ten articles. 



a Bull, de l'lnstitul Oceanographique, no. L13, Mars 1908, p. I, figs. I 6. 

 b Amph. of Pearl Oyster Fisheries, 1904, p. 261, pi. Ill, fig. L9. 

 cSeeAnn. Mag. Nat. Eist., ser. 8, vol. 6, L910, pp. 31 32. 



Proceedings U. S. National Museum, Vol. 38— No. 1767. 



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