184 R. E. SNODGRASS. 



The tergum of the hypopygium is a triangular plate, with the 

 apex directed caudad. The sternum is similar in shape to the ter 

 gum, but is larger. The tergum and sternum are widely separated 

 on the sides of the segment by the very large pleura. Each of these 

 plates is oval or rhomboidal, strongly convex on the outer surface, 

 and bears distally, on the inner face, a long, densely chitinous, bent, 

 blunt spine directed inward and forward. All species of the Tipu- 

 lidse have lobes of some sort born on the ends of the pleura; these 

 are collectively termed the apical appendages. 



The guard of the penis (fig. 8) is a large flat plate on the floor of 

 the genital chamber. The anterior margin is deeply emarginate, its 

 posterior margin graduated and produced medially into a short 

 blunt process. A deep groove extends along the mid dorsal line of 

 both the body of the plate and the posterior prolongation. The 

 penis most probably resembles that of the following species and 

 lies in the groove of the guard. It was not found in the specimens 

 dissected. 



Arising from the lateral walls of the genital chamber there is, on 

 each side, a biramous appendage, shown in fig. 11. The upper arm 

 is the longer and has its distal half bent upward. The lower arm 

 projects downward and caudad, and then is curved upward. The 

 recurved parts of the two lower arms lie in the notch on the ante- 

 rior edge of the guard of the penis. These two bifid processes are 

 here, as explained in the introduction, tentatively called the second 

 gonapophyses. The guard of the penis is regarded as being formed 

 of two rami converging and fusing beneath the penis, which consti- 

 tute the first gonapophyses. 



Antocha sp. inc. (PL VIII, figs. 3, 6, 7). 



This species is very similar to the last, but the hypopygium differs 

 externally in having the pleural lobes slenderer and less convex. 

 The tergum also is widely truncate and concave posteriorly. The 

 apical appendages are two in number on each side, and they are 

 thicker than in A. opalizans. 



The internal parts of the hypopygium differ more in the two spe- 

 cies than do the outer parts. The guard of the penis consists of a 

 small triangular plate, with the lateral edges turned up so as to 

 make a short triangular trough in which lies the distal half of the 

 penis. From the basal angles there diverge anteriorly two wide flat 

 arms (fig. 6). 



