williston: dialysis and tkiptotricha. 265 



Length of the body 10 inillim. ; of the wings S ' 3 millim. One 

 specimen." 



It is very fortunate for Dipterology that so able a student as Mr. 

 Austen is engaged in the study of the British Museum diptera. We 

 can now confidently expect to learn much that will be of value con- 

 cerning Mr. Walker's unrecognizable species and genera. 



This much results from the above facts: The genus Ag/io/oinyia is 

 absolutely identical with Dialysis and must be abandoned. Is the 

 presence of but four posterior cells a good generic character? I can 

 not say. (lenera are founded in allied families on the same or simi- 

 lar grounds, and I have yet to see a specimen of Dia/ysis (in the 

 sense of Agnotomyia) in which the character is variable. Still, from 

 the fact that there are other species with the same tibial character and 

 four posterior cells, and especially because there seems to be a ten- 

 dency to variation in the venation of Triptotricha, I am inclined to 

 give up this character, and base the genus for the present on the 

 tibial character alone. With this conclusion, both Dialysis and 

 T7-iptotricha may be retained. If Dialysis is maintained upon the 

 wing character, then I believe it would be justifiable to place D. 

 rufithorax and the following new species in a new genus. 

 The following species belong to the genus Triptotricha: 



T. disparilis Bergroth. Wien . P^nt. Zeil., 1889, 2i)G: and 1892, 1()2. 



T. lauta Loew, Centur., X, 15. 

 The following in Dialysis: 



D. dissimilis Walker, Iiis. Saund., \. 



D. rufithorax Say. .). Acad Phil., III. :;<>; Compl. Wr., II, 5(). 



D. elongata Say, Journ. Acad. Phil, III, 41; Compl. Wr., II, 58 

 {Slygia); Anthrax, Lonmtia Wiedemann; Aynotomyia Williston. 



D. aldrichi Williston, nov., infra. 

 The following species are indeterminable at present: 



D. dispar Bigot, Ann. Soc. Ent. Fr., 1889. 



T. discolor Loew. Borl. Ent. Zeit , 1871, 379. 



T. fasciventris Loew, 1. c, 380. 



Dialysis aldrichi n. sp. 



Male. Eyes sejjarated by linear space, which, with the vertical 

 triangle, is black; frontal triangle with yellow pubescence. First 

 joint of the anteiinai blackish; second joint reddish yellow; third 

 joint and the arista black; first two joints with black hair. Proboscis 

 yellowish pile; humeri yellowish dusted. Pleurct; shining black, the 

 upper part of the meso- and metasternum white. Halteres yellow, 

 the knob blackish. First four segments of the abdomen yellow with 

 a black anterior cross-band, expanded triangularly in the middle to, 

 or nearly to, the hind margin; remaining segments black with the 



