190 R. E. SNODGKASS. 



These four plates, arising thus two above and two below the base of 

 the penis, and converging about its tip, apparently are the four gona- 

 pophyses. 



Liiniiopliila rufibasis O. S. (PL IX, figs. 17, 21, 22, 23, 25). 



The hypopygiuni forms but a slight enlargement of the abdomen. 

 The body of it is a narrow ring. The tergal part is deeply notched 

 and the corners of the notch are produced into small blunt points 

 (fig. 23). The pleura are very large lobes, convex on all sides, 

 membranous on the inner surfaces. Each bears distally two apical 

 appendages, one of which (figs. 22, 28) is diiected posteriorly and 

 the other inward and anteriorly. 



The penis arises from a large biramous base on the floor of the 

 genital chamber (fig. 17, h,]j, fig. 21). Beyond the base it is re- 

 ceived into the guard (|j, g). This is a large, compressed, oval 

 structure, with the distal end produced into a decurved prolonga- 

 tion. It is composed of two thin lateral shells continuous with each 

 other below, and united above in a suture, forming thus a capsule 

 entirely enclosing the penis. The latter forms a slender curved tube 

 within the guard. 



The second gouapophyses are two long, slender, tapering, decurved 

 rods, arising from the anterior wall of the genital chamber and ex- 

 tending posteriorly a little beyond the guard (fig. 23, gon. 2, and 

 fig. 25). 



In this species there is a well developed anal tube or tenth seg- 

 ment (fig. 23, a, t) arising from the roof of the genital chamber and 

 projecting out of it posteriorly. 



Limnopliila qtiadrata O. S. (PI. IX, fig. 18; PI. X, fig. 34). 



The abdomen is slender and cylindrical, the hypopygiura does not 

 form an enlargement. The eighth segment is a simple narrow ring. 



The body of the hypopygium consists of a perfectly simple ring, 

 wider than the eighth segment, undivided by sutures, having only a 

 wide notch in the jwsterior margin below. The pleural lobes are 

 somewhat elongate, and each bears terminally two slender, tapering 

 apical appendages directed inward and forward. 



The guard of the })enis is a long tube greatly swollen in its basal 

 half; slender, cylindrical or tapering and curved upward in its ilis- 

 tal half (figs. 18 and 34, ;>, g). The length and the curve of the 

 distal half vary considerably in dirterent specimens. In souie the 



