ART. 11 SOME BURGESS SHALE FOSSILS — HUTCHHSTSON 17 



that in life they were directed posteriorly, 3 a little inward and 3 

 a little outAvard, and that the apex of the leg figured is somewhat 

 twisted. The apices of the legs of (6) show traces of a central 

 structure represented by a minute dark longitudinal elongate spot, 

 a similar more triangular area can be seen (fig. 4&) in the fourth 

 right leg of (a). These areas of dark material are very indefinite, 

 but probably represent a similarly placed triangular region free 

 from large papillae, situated above the foot in modern Onychophora, 

 as Pei'lpafopsis capensis (Grube). From the side of some legs, 

 notably the third left of the type (Walcott, 1911, pi. 23, fig. 9), and 

 the posterior pair (fig. 4(?) of {a) a spurlike elongation can be seen 

 lying as if it was projecting from the internal surface of the leg, 

 pointing forward in the former specimen, backward in the latter. 

 These structures are presumably the straight setae of Walcott, the 

 claws being his hooked setae. They are. however, not composed of 

 the whitish material into which the claws have been transformed, 

 but are fossilized exactly like the rest of the body and therefore 

 were probably soft walled. Since they are found on both third and 

 last legs they presumably occurred on all the legs but were hidden 

 during fossilization. The 10 posterior appendages of Aysheaia 

 pedunculata therefore consisted of wide slightly tapering annulated 

 limbs bearing six apical claws and possibly other terminal struc- 

 tures, and a ventral or internal organ to which the name "internal 

 process '" may be conveniently applied. The bases of the unexposed 

 legs on the left side of {h) are presumably represented by the svrell- 

 ings in the middle of the body above each leg. 



Branched appendage. — The segment immediately in front of the 

 first pair of legs carries a pair of appendages which in the dorso- 

 ventrally compressed specimens lie in an exactly comparable posi- 

 tion to the legs. In specimen (6), however, these appendages seen 

 from the side, are apparently directed forward and downward 

 on the right, backward and upward on the left. The head is prob- 

 ably twisted, but there can be little doubt that the appendages in 

 question Avere inserted at a somewhat higher level on the body wall 

 than were the following 10 pairs of legs. The position of fossili- 

 zation in (&), moreover, strongly suggests that they were very mobile 

 and could take up a variety of positions. This pair of appendages 

 differs radically from the legs in not possessing claws and in 

 being furnished with a number of branches or processes. In the 

 left-hand branched appendage of {h) two apical and two basal 

 processes are distinguishable (fig. 4(^), and there are indications 

 of two papillae in the middle region. In the left-hand appendage 

 of (a) and in that of the type three processes at least are present. 

 In (6) all lie on the anterior side of the appendage, in («) two 



