354 Proceedings of the Royal Society 
one form before them, when they describe three or four apparently 
different ones, and trace them to different species. Thus, such 
terms as unisulcus , bisulcus , trisulcus , unisulcus corrugatus , and the 
like, instead of indicating so many distinct species, may, in reality, 
express the varying form of the track of one only. Perhaps, even 
the Hitchcocks’ in their magnificent works on ichnology have not 
given due weight to this consideration.* 
The slabs laid on the table have been examined with great care, 
in the hope of detecting traces of hairs, setae, or any other charac- 
teristic marks of true recent annelids. But neither hairs nor bristles 
have been found. On most of the slabs, however, markings occur, 
which I am inclined to regard as the outlines of organs analogous 
to the gill-leaves of such forms as Phyllodoce. These are worthy 
the attention of naturalists. They are numerous, and have not, I 
think, been observed before. While occurring on the same surface 
as the outlines and tracks of the organisms, only in one instance 
they seem attached to them, but even in this case the association 
is doubtful. See Plate IV. fig. 2, for an outline of some of these 
markings. In one case, in which a good duplicate was obtained, 
distinct traces as of a fringe appear. An enlarged rough outline 
of part of this fringe is shown on the Plate, IV. fig. 4. On the 
same specimen a good many annulate pointed objects occur, two of 
which are represented at a and b fig. 2. 
There can be no doubt that both tube inhabiting and errant 
Annelida existed in palaeozoic time — traces of some being found 
even in the Laurentian rocks — though little is known of their true 
nature and relations. The genera conchiolites , cornulites, serpulites , 
spirorbis , and trachyderma, may be said to complete the list of the 
former, and the genera arenicolites, crossopodia , myrianites , and 
nereitcs that of the latter. But even some of these generic designa- 
tions are open to criticism, or cumbered with doubt, and it is 
questionable if, in any of these cases, we have a true representation 
of the animal itself. Such considerations add to the value of the 
specimen now under notice. It has no resemblance to any of the 
forms just named. The first examples on record having some 
* <f Ichnology of Massachusetts.” By Edward Hitchcock, Boston, 1858. 
“ Supplement to the Ichnology of New England.” Edited by C. H. Hitch- 
cock, Boston, 1865. 
