226 R. E. SNODGRASS. 



The anal tube arises from the anterior wall of the genital cham- 

 ber just below the lower edges of the posterior lateral tergal lobes. 

 These two lobes on the sides, the anal tube below, and the under side 

 of the tergum above, enclose a distinct dorsal division of the genital 

 chamber between them. A narrow rod of chitin extends across 

 its roof between the anterior ends of the tergal lobes. From this 

 bar there hangs downward in the chamber a free bifid chitinous rod. 



The central vesicle is of the ordinary shape. It is so situated, 

 however, that its posterior arms project ventral ly, and its anterior 

 end is dorsal. Hence, the penis curves first dorsally and anteriorly 

 from it. The guard of the penis is a short, curved appendage, thick 

 basally, slender and pointed terminally, and grooved lengthwise on 

 its upper surface. 



Tipiila sulphnrea Doane (PL XII, fig. 66). 



The hypopygium is externally of very simple structure. There is 

 no division between tergum, sternum or pleurum, nor is there a 

 pleural suture. The sternum is deeply emarginate, but each edge 

 of the V-notch carries a narrow lobe attached along its entire length. 

 The tergal margin bears two small median darkly chitinous knobs. 



There are two apical lobes on each side. The first is short, slen- 

 der, cylindrical and curved upward (fig. 66, A). The second (B) 

 is wide and fiat. On its outer side a fiat lobe covers its anterior edge 

 basally. Near the centre of the inner face there arises an unciform 

 process that projects inward. 



The penis curves immediately downward and posteriorly from the 

 central vesicle. The guard is simple and stylet-like, with a dorsal 

 groove. 



Genus CTEIVOPHORA Meigen. 



In the structure of the hypopygium this genus scarcely differs 

 from some of the species in Group III of Tipula. It is placed at 

 the top of the family by systematists, and logically following the 

 system by which the species of Pachyrrhina and Tipula have been 

 arranged in this paper, it must be assigned this position if classified 

 by the structure of its hypopygium. 



Ctenopliora angustipennis Loew (PI. X, figs 46, 47, 48, 49). 



The eighth segment is high and comparatively short, but is not 

 specially modified, nor is its sternum produced beneath the hypopy- 

 gium. 



