AMERICAN DIPTERA. 217 



The central vesicle (fig. 97) is hemispherical. Its posterior arms 

 are long and slender, the anterior lateral lobes are large, wide, 

 rounded plates. The penis is extremely slender, almost hair-like, 

 and runs forward to the third abdominal segment before turning 

 posteriorly. 



The guard of the penis (fig. 95, p. g.) is an elongate pyriform 

 structure with a median groove along the dorsal side. It is sup- 

 ported on a rather complicated framework of chitinous bars. A flat 

 chitinous tongue like process, pointed distally, arises from the ven- 

 tral side of the guard and projects posteriorly below it. The sup- 

 porting framework alone is shown in figure 99 ; a is the ventral 

 tongue of the guard with the latter removed from its proximal end. 

 On each side there is a long plate bent into a right angle (6). One 

 arm of each lies along the side of the guard, the other projects out- 

 ward and downward from the distal end of the first. From the. 

 angle a tapering plate (c) runs posteriorly, inward and downward, 

 and unites with the ventral tongue of the guard. The latter is con- 

 nected in a similar manner with the middle of the longitudinal arm 

 by a tapering bar (d). The guard itself is, thus, supported only by 

 its ventral tongue, this being attached to the plates on each side by 

 the two pairs of transverse connectives. 



Tipula lamellata Doane (PI. XII, figs. 73, 76, 77). 



The eighth sternum is prolonged posteriorly beneath the hypopy- 

 gium and bears at its truncated end two brushes of long hairs 

 (fig. 77). 



The tergum of the hypopygium has almost the shape of the capi- 

 tal letter A with the apex cut off (fig. 73). It consists of two nar- 

 row plates diverging widely posteriorly and connected near their 

 middle by a transverse crescentic bar of chitin. The concave pos- 

 terior border of this bar forms the posterior margin of the tergum. 

 The area in front of it is membranous. The pleural plates are 

 small. Each (fig. 77, pi.) has the appearance of being an append- 

 age on the posterior rim of the sternum. It consists of a short wide 

 basal part and a free tapering but blunt process projecting poste- 

 riorly. To the inner side of its base is attached the apical appendage. 



There is only one apical appendage on each side and this is the 

 second (fig. 76). It is a wide, flat plate arising from a narrow base 

 but rapidly expanding distally. It bears a sharp-pointed projection 



TRANS. AM. ENT. SOC. XXX. (28) JULY. 1904. 



