1914.] NATURAL SCIENCES OF PHILADELPHIA. 51 



noted that there is on the last division an unusually large spine, set 

 well towards the distal end. There is also a small blunt spine with a 

 large comb-like fringe on its outer margin, placed about in the 

 middle of the second large division of the male antennae. The re- 

 maining spines are rather smaller than in other species. On the 

 joints of the first division there are present, on the under side, the 

 usual long, blunt, finely plumose sensory structures. 



The second antennse are very short and broad. The long curving 

 seta of the basal segment I have never found to be evenly plumose 

 as Schmeil shows it. It 'is usually armed with a row of short spinules 

 on each side of its distal three quarters, while the first quarter bears, 

 only on its upper side, an uneven row of longer spinules. The 

 second segment bears on its outer side a double row of delicate spines, 

 and on its upper side a fringe of spinules and near its distal end a 

 peculiar spine. The distal half of this spine is curved and bears on 

 its upper side a comb-like fringe of fine spinules. The smaller spine 

 on the distal end of the third segment has this same peculiar curve 

 and fringe. The curved setae at the top of the fourth segment are 

 short and very broad. 



The four pairs of swimming feet are all three-segmented, both 

 spines and setae are well developed, and the outer edges of the first 

 and second' segments of each ramus bear rows of heavy spinules. 

 The armature is most variable. For example, I have found on the 

 outer ramus of the first pair either three or four spines and five setae. 

 Again in the second pair on the corresponding ramus I have found 

 four spines with either four or five setce. In another case I have found 

 on the outer ramus of the fourth foot of the right side, three spines 

 and five setae and on the same ramus of the opposite side four spines 

 and four setae. Furthermore, the armature of the inner ramus of 

 the second and third pairs of swimming feet differs consistently from 

 that given by Forbes, in the presence of an extra seta on the inner 

 side. This seta is very obscure and may be overlooked on account 

 of the long spinules on the same side of the ramus, but its existence 

 can be positively identified by its position and by the fact that, 

 though it is often not much larger than the accompanying spinules, 

 it is the only one that is plumose. I give this rather lengthy dis- 

 cussion of the swimming feet merely as an example of the armature 

 not being constant nor reliable as a point of differentiation of species. 

 (See Introduction.) The following is an average armature for the 

 local specimens: 



First pair — outer ramus, three spines, five setae; inner ramus, one 

 seta, one spine, four setae. 



