— 49 — 



is abruptly somewhat bent, with the distal part longer and 

 more slender than the proximal and flatly curved with 

 the concave outer margin serrate, in N. megalops to the 

 bend, in AT. difficilis to a little from the bend (Fig. 18) ; the 

 proximal saw-teeth are fine and the distal much larger in 

 both species. But in N. difficilis the serrate part is slightly 

 more than half, in N. megalops considerably more than 



half, of the inner margin ; furthermore the saw-teeth in 

 N. megalops, in which 44 were found, are much more 

 numerous and especially along the more proximal portion 

 placed much more closely together than in N. difficilis, in 

 which I found 27 saw-teeth. In both species the proximal 

 process is shorter than the terminal, w r ith its distal part 

 slender, straight and finely serrate along its outer margin, 

 but in N. difficilis the serrate part is much less, in N. me- 

 galops only a little less, than half of the inner margin of 

 the process, and what is of special importance, in N. me- 

 galops this process reaches at most the middle of the 

 serrate margin of the terminal process, but in N. difficilis 

 much beyond the middle of that distal part. The last- 

 named character is easily seen by cautiously unrolling a 

 copulatory organ under a dissecting microscope without 

 separating it from the animal. 



lobe of N. difficilis n. sp 



(210) 



