CR USTA CEANS OF NICKAJACK CA VE—HA Y. 429 



Order AMPHIPODA. 

 Family GAMMARID.E. 



Genera NIPHARGUS and GAMMARUS. 



lender the generic name NiplianiuH Schiodte I pUu-o the .speeies 

 described as Crangonyx antetinatus, by Dr. Packard,' as I tind it 

 iiorees much more closely with that genus than with Cramjoin/.r or 

 (iarivrnarus. As remarked by Chilton," the genera OnnKjorn/.i' and 

 Xiphargus are very closely related, ditiering only in the fact that the 

 telson in the latter genus is divided, while in the formoi* it is entire. 

 In the present species the only parts in which there is a difference 

 from the other species of the genus are the last pair of uro]iods, which 

 do not have the outer branch excessively elongated. 



Although the various species of Niphargus are well-known inhab- 

 itants of wells, springs, and subterranean water courses in the Old 

 World, no species has heretofore been described from North America. 

 That I do not claim the honor of being the first to recognize the genus 

 in this country is due to the retentive memory and apparently limit- 

 less information of my esteemed instructor and friend, Dr. Theodore 

 N. Gill, who has just called my attention to a mention of it in a list of 

 the Crustacea of the District of Columbia, published in a rather obscure 

 work as long ago as 1861.^ The name was evidently applied with 

 some doubt, as it is followed b}- an interrogation mark. • Dr. Gill was 

 also able to give some interesting information regarding this citation 

 and the specimen upon which it was based. The list of crustacea, it 

 seems, was furnished b\^ Stimpson, to whom, however, no credit is 

 given in the book. The specimen (for according to Dr. GilFs recol- 

 lection there was but one), which is called Niphargus, was sent in 

 from some well near Washington, and in conversation Stimpson 

 expressed himself as certain that it belonged to that genns. Unfor- 

 tunately, no further reference was made to the species, and no other 

 specimens have been obtained. 



That other species of this genus have been observed in North Amer- 

 ica I do not doubt, but they seem in all cases to have been described 

 as Crangonyx. The two genera are very closely related, and differ 

 apparently only in the telson, which is entire in Crangonyx andi divided 

 in yjphargas. Crangonyx hlfurcus O. P. Ha}' is a Niphargus; C. 

 luclfugm O. P. Hay, C. Packardi Smith, C. tenuis Smith, and C. mt- 

 7'eii8 Smith seem to be correctly placed; C. gracilis Smith has the telson 

 slightly emarginate, but' not divided to any appreciable extent in any 

 of the specimens which I have examined. C. niucronatus Forbes is 



■ ' Am. Nat., XV, 1881, p. 880. 

 ■Trans. Linn. Soc. I.ond., 2d ser., VI, pp. 218-220. 

 ^Phelpa'a Washington Described, 1861, p. 34. 



