}\()rtli, Aiiu'iii-dii ('ciitnq)ti(/i(/ic. '237 



a fresli-water centropa.uid closely resembling- the inavine 

 genus Cdhoiii-s, aiid until 18(S9 L. inacnirns was the only rep- 

 resentative known. In that year Poppe described (de Ciuerne 

 et Richard, '891)) a new species, L. sinoisi^, from China. 

 The latter, so far as now known, is a purely fresh-Avater form, 

 and L. )n(icn(n(s was at first so regarded, but in Asiatic and 

 European countries it has l)een found to occur in both fresh 

 and salt water, — in America it has as yet been found only in 

 fresh water, — and further search may show that /.. suicui^is, 

 too, is common to liotli. L. iiKicrnnis is the only American 

 representative of the genus, but it was deemed best to in- 

 clude i^inoi-sis in this paper, thus making the revision of the 

 genera treated complete. 



As already stated, the genus is represented liy only two 

 species, nuiminis and niiiciisix. The former is common to 

 America, Europe, and Asia, liaving been found in the river 

 Jana (in East Siberia), in the Caspian Sea, in the x\rctic 

 Ocean, in the lakes of northern Norway, Sweden, and Fin- 

 land, and in the deeper northern lakes of North America ; 

 the latter, siiieitsin, has been found only in eastern China. 



Marsh, in his "Limnetic Crustacea of Green Lake" ('97), 

 records some observations on the habits of LtmKocdhdinx, 

 and states that it is repelled by l)right light and high tempera- 

 tures, and hence performs diurnal migrations which are more 

 pronounced in cold weather. It seems to have tv.'o periods 

 of maximum occurrence. May and November, but is found at 

 all times, although never very abundantly. Li March and 

 April most of the individuals are immature. 



To my knowledge Limnovcdanus has never been found with 

 an egg-sac, differing in this respect from Osphnini'icnm and 

 DiaptoviKS but agreeing with Kphchiird. The spermatophore, 

 a slender tubular structure, adheres to the female for a con- 

 siderable time after attachment. 



From a practical and economic standpoint Limnoralaniis 

 is of importance as contributing to the first food of ('ore(ioinis 

 cbijjciformis (Forbes '83a), of Lnhulcxf^ic^ >iicculiis^ , and 

 probably of other lake fishes. 



*See Forbes "Oii the Food Ixclations of Fresh-water Fishes: a Sumraarv and Dis- 

 cussion.' Hull. 111. State Lab. Nat. Uist.. Vol. II., Alt. Vin.. p. 5y,'. 1885. 



