298 
On tlio weathered surfaces of the hardened and undecomposed shale, the remains 
of these burrows present a most peculiar appearance, all traces of the tube having 
disappeared, whilst the infilling portions, often, in this case, of a different colour to the 
surrounding matrix, are left as a series of more or less disjointed, infundibuliforra stains. 
This is the longitudinal aspect, but when seen in section the circular outline is quite 
apparent, and as both longitudinal and transverse sections are visible on the same 
specimen no doubt can be entertained of their connection with one another. In our 
present limited knowledge of the nature of the numerous tracks and markings found on 
the surfaces of the older rocks, it is difficult to offer a reliable explanation of these bodies. 
It has been customary to make the Annelida a kind of refuge for the destitute in such 
eases, but the writings of the late Prof. Perdinand von Roemer, Mr. Nathorst, and others 
have probably given the death-blow to this loose method of generalisation. A general 
epitome of the subject will be found in an article by Prof. H. A. A icholson and the 
AV riter,* hut no better explanation of how a large number of these tracks are formed has 
been offered than the lucid .and exhaustive description by the late Albany Ilandcock of 
vermiform markings in the Carboniferous Lime.stono of the North of England. f This 
eminent Naturalist has suggested the analogy of his vermiform markings to the burrows 
of certain Amphipod Crustaceans, named Krbyeria arenaria, Bate, and Sulcator 
arenariiis, made in shore-sand under his own eyes. Speaking of certain of the fossil- 
tracks, be says “ Full-sized specimens are half an inch wide, and are composed of a 
series of nodules, which give them an articulated appearance. The nodules, which vary 
a little in size, are usually about half an inch long, and are not very symmetrically oi 
regularly formed. Consequently the surface has generally an imperfect or worn 
character. The extremities are not often seen ; they are abruptly and irregularly 
rounded.” 
These remarks w'ere supplemented by the following “ The specimens . . 
are characterised, as we have seen, by a remarkable nodulous or articulated appearance 
which has been supposed to indicate the presence of rings of some Annelide ; and, indeed, 
were it not for the light derived from the Crustacean tracks on our shores, it would not 
be easy to conjecture a more plausible explanation. We have seen, however, that a 
variety of the track of Krbyeria arenaria has the ridge of sand thrown up, broken into 
nodules, giving to it a beaded character. This, on a small scale, has a considerable 
resemblance to these nodular forms. But a much nearer approximation is found with 
nodulous tracks of Sulcator arenarius It may therefore be assumed that 
the animal whichmade these nodulous tracks, like our small Crustacean, pushedalongin its 
path, step by step, resting awhile after each advance, but that, instead of moving in each 
horizontal plane, it alternately rose and sunk a little ; consequently, a series of nodules 
was produced, and the track acquired its peculiar articulated appearance. This explana- 
tion is strengthened not a little when we look at the side view of the cast of this track. 
The nodules are then distinctly observed to be imbricated, and to pass, very much 
inclined, right through the substance from top to bottom.” 
Without implying that the Rockhampton markings are produced by Amphipods, 
these quotations are simply given to show that it is not necessary to call in the aid of 
the Annelida for their exijlanation. The only Crustaceans known to occur in these beds 
are Trilobites, but the tracks ai’e not such as have been hitherto ascribed to these 
animals. Other organisms aro capable of causing such raised tracks, as evinced by 
* Mon. Sil. Foss. Girvan in Ayrshire, 1880, Pt. 3, p. 304. 
t “ Remarks on certain Vermiform Fossils found in the Mountain Limestone Districts of the 
of England.” Ann. and May. Nat. Hist., 1858, ii., p. 143 ; Tmns. Tyncsiflc Nat. Fkid Club, 1858, iv., 
p. 17. 
Xorth 
Pt. ii 
