♦ •>v. 



'22() Illinois Stiiff Tj(ihi)}-(itt)yii of Xiitiiral Jlistori/. 



the species in question ilitfer, however, so considerahly in 

 these two articles that, as Schmeil ('08) says, nothing certain 

 can l)e said of this species until Herrick declares himself as to 

 wliicdi of the two sets of drawings are correct. Schmeil regards 

 Herrick's form as possil)ly a new species. The recent dis- 

 covery of a new species of -this genus, Euri/fcniord lierdmani 

 I. C. Thompson and A, Scott, in the St. Lawrence Eiver and 

 Gnlf removes all douht as to the presence of the genus in 

 American waters.* 



Of the three genera treated in this paper, OspliriDitictiiit, 

 containing a single species, and Episrlmrd, containing three' , 

 are, st) far as now known, confined strictly to North America 

 and are strictly fresh-water in their hahitat. ()sj)]t,r(iiiticuni 

 is ordinarily found in shallow or stagnant lakes and ponds 

 (Forhes) or in running water (Herrick), while Kpisclnird 

 occurs, as a rule, in deep clear lakes. The genus LimnocidanuH 

 is peculiar in its hahitat. One of the two species, L. i^lnoisis 

 Poppe, from China, is, so far as known, a strictly fresh-water 

 form, while the other, L. nuimirus Sars, although found as 

 yet in America in freshwater only, occurs in Europe and Asia 

 in l)()fh fresh- and salt-water lakes and in the ocean. Since 

 there are only these two species known, it was thought hest 

 to treat hotli in this paper. 1j. (jriiiuddii de Guerne is re- 

 garded l)y the writer as a synonym of /.. iinicniniH Sars*, for 

 reasons given in the discussion of the latter species. 



A l)rief discussion of the structural similarities and differ- 

 ences indicative of the relationships of the genera Osphranti- 

 ciim, Lii)iiio<-(d(iin(s, Diaptonins, and Kpischura may properly 

 precede this paper, special attention heing given to characters 

 whicli are regarded as of generic or specific value. . 



Gieshrecht, in his "Monograph" ('1)2), gives sx)ecial rank 

 to the structure of the first pair of antenna as a distinguish- 



■i-See "On the FlanUtou nollected continuously during two Traverses of the Xortli 

 Atliuuic in the Sunnuer of 1897; with Descriptions of New Copepothi: and an Ap- 

 ])endix on Uredsing in Puget Sound." By W . A. Herdman, I. ('. Thompson, and An- 

 drew Seoit. Trans. Liverpool Biol. Soc, S'ol. Xn. (1S97), p. T9. 



■\E- fluvialilis Herrick is not considereil one of these. 



iThe Z lologisches Oentratb/att (-hihr^^.. HI., p]). 481-4S3) contains a review of an 

 article by N. Zograf entitled " Essai d'Kxplication de I'orlgine de la Faune des lacs de 

 laHussie d'Kurope"in which a reference occurs to L. macronyx O. (), S. This is 

 (M'obably an error, since it is the only reference to a species of that name which 1 

 iiHve been able to tind. 



