226 [April 



At the same time, these subdivisions were better defined and their 

 relations to each other more clearly established, than was done in 1859. 

 Among the introduced innovations, the most important were the fol- 

 lowing : — 



1. The genus Limnobia, as defined in my first paper, was broken up 

 now in the genera : Geranomyia, Rhipidia, Dicranomyia, Limnobia 

 and Discobola. The last genus comprises the European Limnobia 

 annulata Lin. and the American L. argus Say, both distinguished by 

 a supernumerary cross-vein between the sixth and seventh longitudinal 

 veins. 



2. The genera Cytindrotoma, Triogma and Ehalacrocera, all new 

 for North America, were located in the artificial tribe of Limnobina 

 anomala, which was subdivided in three groups as follows : 



a. Rhamphidiseformia. 



b. Cylindrotoms&formia. 



c. Anomala. 



3. The name of Limnobiorhynchus Westw. was dropped for the pre- 

 sent, and that for reasons to be shown hereafter, and the generic name 

 of Toxorhina Loew was resumed. A new genus, Plectromyia was 

 added to the group c. (Anomala vera?) 



4. Epiphragma nob. was altogether separated from Limnophila. 



5. The genus Arrhenica was united with Eriocera, under the latter 

 name, as the distinctions, previously established between the two genera 

 were found to be insufficient. Thus Eriocera will contain now species 

 with I0112; and with short male antennae, similar in this to the related 

 genus Anisomera, which likewise contains two groups of species, based 

 on the same character. 



6. The genus Penthoptera, recently introduced by Schiner (Fauna 

 Austriaca, Dipfera, II, p. 534) was found to occur in the United States 

 and consequently admitted. Its relationship to Eriocera is very close 

 and the differences are not easily defined ; they principally consist in 

 the proportionally much more elongated cells of the apical portion of 

 the wing. The 9 antenna; of this genus, which I have had occasion 

 to count on a living specimen, are ten-jointed. 



7. Two new genera A&trolabis and Rhaphidolabis were introduced 

 among the Limnobina pediciseformia. 



The terminology used in my former paper, especially with reference 

 to the neuration of the wings, was abandoned, and that adopted by 

 Mr. Loew in his publications introduced in its stead. 



