AMPHIPODA FROM COSTA RICA. 



By Rev. Thomas R. R. STEBRiN(i, 



Fellow of the Royal Society. 



The specimens here described were sent to nie for determination by 

 the United States National Musemn, and represent two new species. 

 They were collected by Prof. P. BioUey, of the National Museum of 

 Costa Rica. 



Family TALITRID^. 



1900. T<(litri(Lv Stebbing, Fauna liavvaiiensis, II, p. 527. 



TALORCHESTIA FRITZI, new species. 

 Plate LX. 



The largest of the male specimens have the perteon transversely 

 corrugated, each of the segments showing two folds, except the first 

 segment, which has a single fold. All the specimens, however, 15 in 

 number, have the integument brittle and most of the muscidar parts 

 shrunken. The exceptional corrugation, therefore, in the large male 

 examples ma}^ not be a natural feature, but merely due to conditions 

 experienced since their capture. In the synoptic table published four 

 3^ears ago " for discriminating the genera of the Talitrid{\?, at that time 

 called Orchestiida?, the leading distinction between Orchestia and Talor- 

 chestia rests on the fact that in the former the first gnathopods of the 

 female are subchelate, whereas in the latter they are simple. So far 

 as this distinction is concerned, the present species clearly belongs to 

 Talorchedla. The sixth joint of the limb in question has no distal 

 widening to furnish a "palm" upon which the finger can close. In 

 Orchestia the widening is seldom or never very great, but how far it 

 may be reduced without effecting generic change has not yet been 

 determined. 



The eyes may be described as rotundo-quadrate, with a diameter 

 nmch larger than the interval between them. 



First antenna} of male have the middle joint of the peduncle slightly 

 the longest, the five-jointed iiagellum about half as long as the pedun- 

 cle, the whole appendage being subequal in length to the last joint m 

 the peduncle of the second pair. In the female the flagellum has three 



«Trans. Linn. Soc. London, Zool., 2d ser., VII, Pt. 3, 1899, p. 397. 



Proceedings U. S. National Museum, Vol. XXVI-No. 1341. 



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