128 Mr. F. A. Bather o« a 



the frroove is relatively smooth, iu other places the segmental 

 markings and papillaj are clearly seen to rim across it. The 

 apposition of these two grooves would form a tunnel of circiihir 

 section ; but before the sandstone was split open this tunnel 

 was filled with a hardened mud of very fine grain and a pale 

 grey colour. The appearance is most easily explained by 

 regarding it as the gut of a mud-eating worm ; the muddy 

 core, of which considerable stretciies are retained in one or 

 the other counterpart, is the remains of the animal's last 

 meal ; the smooth lining of the groove, occasionall}' pre- 

 served, is the thin wall of the gut ; the groove itself, seen as a 

 ridge in a wax squeeze, represents the outer skin of the animal 

 raised in a fold over the full gut (fig, 2). As a rule, the 

 core is marked by sligiit constrictions into segments corre- 

 sponding with those of the integument, and perhaps due to 

 pressure from the inturned walls of the segments. The 

 surface between the segmental constrictions may be smooth or 

 marked by elevations corresponding with the papillae of the 

 integument. In some places the calcified substance of the 

 papillae is still attached to these segments of the gut, instead 

 of to the outer skin. There are occasional slight longitudinal 

 ridges, indiqating folds in the wall of the partly-filled gut, due 

 to pressure. 



The gut itself was not confined to the region of the fossil 

 now marked by a groove or its core, for a darker tract indi- 

 cates its former extension down the stem of the 2, though it 

 is im{)Ossible to say how far it went. 



This gut-structure has not ))een mentioned as occurring in 

 any Ordovician species, but Ulrich^s figure of P. simple.v 

 shows a dark line or groove down the middle, and there is 

 some slight suggestion of the same marking in the complete 

 figure of P. ornatus. The importance of the gut lies in its 

 confirmation of the view that these fossils were worms of 

 some kind. The apparent tapering towards each end, as 

 observed in many of the specimens, indicates that they were 

 free-moving forms ; unfortunately no distinction between the 

 ends has yet been detected. 



Hitherto the o])inion as to the systematic ))osition of Proto- 

 sco/ex may be exjiressed in the words of Miller and Faber 

 (1892). After giving reasons, drawn cliicfiy from the mineral 

 character and state of preservation, against the fossils being 

 crinoid stems (some of which in many respects they so closely 

 resemble), they add : — " We have no evidence to offer to 

 show that they rcj)resent iho tubes of Annelida, but probably 



