100 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 49. 



The third segment is distinct and unusually well developed. It bears i 

 two spines, the inner of which is shghtly setose and about twice as 

 long as the outer one. The endopodite re^;' hes about to 

 the middle of the first segment of the exopodite and bears 

 two or three small spines near its tip. (Fig. 5.) The 

 spine of the first basal segment of the male fifth feet is 

 of moderate size. The second basal segment of the right 

 foot is about one-fourth longer than wide and bears, at 

 about the middle of its inner surface, a small hyahne 

 appendage. The lateral hair is slender and arises at about 

 the beginning of the distal third of the segment. The 

 first segment of the exopodite is short and its outer mar- 

 ghi is much longer than the inner. At its outer distal 

 angle it bears a hyaline appendage. The second segment 

 is about twice as long as broad, having its greatest width 

 a httle beyond the middle. From this point arises the 

 lateral spine, which is about as long as the segment, nearly 

 straight, and uniformly tapering to a sharp point. It 

 extends in a direction but little divergent from the axis of 

 the segment. Its inner margin is very finely denticulate. 

 This segment has a small crescent-shaped hyaline elevation 

 about the middle of its posterior surface. The terminal 

 hook is considerably longer than the rest of the exopodite 

 and tapers to a very fine point. It is falciform, witli 

 slightly recurved tip, and is finely denticulate on its inner margin. 

 The endopodite reaches to about the middle of the second segment 

 of the exopodite, and is moderately pointed at the tip, 

 near which are a few very small spines. The left fifth 

 foot, exclusive of the long appendages, reaches a Uttle 

 beyond the end of the first segment of the right exopo- 

 dite, and including the appendages, extends nearly to the 

 end of its second segment. The second basal segment of 

 this foot is about one-fourth longer than broad. There 

 is a small hyaline appendage on its inner margin just a 

 little short of the middle and the lateral hair arises at 

 the end of the second third of the outer margin. The 

 combined length of the two segments of the exopodite 

 about equals the length of the second basal segment. 

 The first segment of the exopodite is about half as wide 

 at its distal as at the proximal end and its inner surface 

 bears a setose pad. The second segment is somewhat 

 shorter than the first and there is a prominent setose pad 

 on its inner surface. The curved terminal processes almost equal 

 the combined length of the two segments. The outer one is blunt 



Fig. 4.— Di- 



A P T O M U S 

 ARAPAHOEN- 



sis. Last 



THKEE SEG- 

 MENTS OF 

 EIGHT AN- 

 TENNA OF 

 MALE. X188. 



Fig. 5.— Di- 



APTOM us 

 ARAPAHOEN- 



sis. Fifth 



FOOT OF FE- 

 MALE. X82. 



i 



