HANSEN: ON SIX SPECIES OF KOENENIA 207 



very short hairs of equal length from its base to the apex. This 

 spine-like seta is met with in all species, but though always 

 robust it is yet more slender in some of the species than in K. 

 Wheeleri. Its place on the outer side of the third metatarsal 

 joint offers an excellent specific character: in K. Wheeleri it is 

 inserted at the end, in Ä'. angusta (pi. 3, fig. 3 f, s) at the 

 base, in K. sianiensis (pi. 4, fig. 2 c, s) at the middle of the 

 joint. I think it probable that this seta has a sensory function. 



c. Other hairs. On the upper side of the metatarsus and 

 tarsus of the first pair of legs (not in the other pairs) are found 

 some very short, biramous hairs. The basal part of them (pi. 

 2, fig. 2 f) is usually shorter than the upper branch, which usually 

 is longer than the other; both branches and sometimes the stem 

 are finely plumose. The number and arrangement of these bi- 

 ramous hairs seem to offer specific characters, but I have not 

 made use of them, as they are too difficult to count with cer- 

 tainty. 



d. Abdominal sacs. As already mentioned Prof. Wheeler 

 discovered paired ventral sacs on the fourth, fifth and sixth ab- 

 dominal segments of K. Wheeleri Rucker. These sacs or pouches 

 are easily seen on the specimens he sent me. AMien the sacs 

 are in what I suppose to be their natural position, they are 

 totally invaginated into the animal. The entrance to each sac 

 is a transverse, linear slit (p in pi. 3, fig. 2 f, representing K. 

 chilensis\ the margin of which is somewhat thickened, and thus 

 the entrance resembles a button-hole. On each of the seg- 

 ments mentioned is found one pair of such slits, situated some- 

 what nearer to the posterior than to the anterior margin of 

 each segment, and the distance between the slits of the same 

 pair is in K. Wheeleri nearly twice as long as each hole. The 

 sac, which is a little longer than broad, is in my material often 

 evaginated quite as a pocket turned inside out (pi. 2, fig. 2 i, 

 p and fig. 2 h, p). I have not been able to discover any muscle 

 to the sacs or any contents within them. Along the anterior 

 margin of each hole four hairs are arranged, and nearer to the 

 median line on the fourth and fifth segments three rather long 

 and very robust set». — In my single specimen of K. ch ileus is 

 I found similar sacs on the three same segments, but here the 



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