128 Mr. F. A. Bather on a 
the groove is relatively smooth, in other places the segmental 
markings and papille are clearly seen to run across it. The 
apposition of these two grooves would form a tunnel of circular 
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 stretches are retained in one or 
the other counterpart, is the remains of the animal’s last 
meal; the smooth lining of the groove, occasionally pre- 
served, is the thin wall of the gut; the groove itself, seen asa 
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 slight 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 
papille is still attached to these segments of the gut, instead 
of to the outer skin. There are occasional slight longitudinal 
ridges, indicating 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 impossible to say how far it went. 
This gut-structure has not been mentioned as occurring in 
any Ordovician species, but Ulrich’s figure of P. simplex 
shows a dark line or groove down the middle, and there is 
some slight suggestion of the same marking in tlie 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 opinion as to the systematic position of Proto- 
scolee may be expressed in the words of Miller and Faber 
(1892). After giving reasons, drawn chiefly 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 :—‘f We have no evidence to offer to 
show that they represent the tubes of Aunelida, but probably 
