196 R. E. SNODGRASS. 



posteriorly, the dorsal end being hidden between the apical append- 

 ages. Each pleurum is a small, elongate, triangular plate lying 

 along the middle of the side of the segment. Its anterior end does 

 not quite reach the anterior margin of the hypopygium. A narrow 

 tapering bar runs downward from the anterior angle of the terguni 

 and meets a similar bar running upward from the corresponding 

 angle of the sternum. There is formed thus a narrow bridge unit- 

 ing the tergum and the sternum in front of the pleurum. The pos- 

 terior end of the pleurum projects as a small rounded lobe into the 

 angle between the tergum and the sternum, and carries the apical 

 appendage (fig. 40). There is only one apical appendage on each 

 side. Each is a long, slender, inwardly curved, club shaped lobe 

 projecting posteriorly and upward (fig. 40, ap. and fig. 45). 



The guard of the penis consists of two elongate, blade-like plates 

 set on edge side by side, arising from the floor of the genital cham- 

 ber. Their lower margins are united by membrane, so that there 

 is thus formed between the two plates a deep narrow groove. This 

 lodges the penis. The latter is a simple, short, straight, rod-like 

 tube, arising from two diverging roots from the lower part of the 

 anterior wall of the genital chamber. The second gonapophyses 

 arise from the anterior wall of the genital chamber. Each is a 

 short blade like plate much resembling a half of the guard of the 

 penis and like it set on edge. In this genus, therefore, the penis and 

 the gonapophyses are much more nearly primitive than in Autocha. 

 If the lower edges of the sides of the guard were not united, we 

 should have the simple condition of the penis surrounded by a pair 

 of processes above it and a similar pair below it. 



Group TIPULiIl^A. 



The group Tipulina is Osten Sacken's Section IX of the Tipuli- 

 dse. It includes, besides several other genera, the Ibllowing genei-a 

 which are described in this paper : Pachyrrhina, Tipida and Cteno- 

 jjJiora. It undoubtedly belongs at the top of the fan)ily. In cer- 

 tain characters of the hypopygium the members are highly special- 

 ized and differ uniformly from all the other genera. 



The characteristic features of the group, in the structure of the 

 hypopygium, are : (1) the fusion of the pleura with the sternum ; 

 (2) the shifting of the base of the penis from the floor to the roof of 

 the genital chamber, and the elongation of the penis in a large curve 



