42 DIPTERA OF NORTH AMERICA.* [PART IV. 



marginal cell have four posterior cells, and there is only one ex- 

 ception to this rule : Cylindrotoma didinctissima and its vicarious 

 North American form — G. Americana ; Meigen's figure represents 

 the wing of the former. Therefore Mr. Walker's description must 

 either refer to some species entirely unknown to me, or more pro- 

 bably, the statement about its wings being like Meigcn, Tab. Y, 

 fig, 5, must be erroneous. Moreover, the name L. turpis cannot 

 be retained, as Mr. Walker himself has described another L. 

 turpis in the Insecta Britannica, Diptera, Vol. Ill, p. 300, in 

 the same year 1856. The description is given in the Appendix 

 to this volume. 



23. Limnobiorhynchus canadensis Westw. = Geranomyia 

 canadensis (comp. below), 



24. Anisomera longicornis Walk. = Eriocera longicornis 

 (comp. below). 



25. Chionea asjjera Walk. = Chionea valga Harris (comp. 

 below). 



26. Chionea scita Walk. ; unknown to me ; the description is 

 reproduced in the Appendix. 



27. Chionea valga Harris, described below under the same 

 name. 



2S.TrichocerabimacuIa Walk. [ ^h^ descriptions of the..e 



29. Trichocera gracilis \Ya\k. ! somewhat doubtful species 



30. Trichocera brumahs Fitch. < ^^'^ reproduced in the Ap- 



31. Trichocera scutellata Say. pendixl ; compare alsothe 



[ genus Trichocera. 



32. Trichocera macuUpennis Meig. ; a European species said 

 to occur in Greenland, according to Stceger. 



33. Trichocera regelatioms Lin. ; also a European species, 

 quoted by Otto Fabricius, as occurring in Greenland, which 

 requires confirmation. 



34. Gynoplistia annulata Westw. I have seen the original 

 specimen in Mr. Hope's collection at Oxford, and have never met 

 with any other, Mr, Westwood's description is reproduced in 

 Appendix I. 



35. Bittacomorpha davipes is described below under the same 

 name, 



36. 3t. Ptychoptera metallica Walk, and quadrifasciafa Say 

 are unknown to me ; their descriptions will be found in the 

 Appendix, 



