NOTES A^'D QrEEIES. 
317 
which not merely demonstrates satisfactorily their organic origin, but indi- 
cates to a great extent the nature of the animal that formed them. In 
pursuing this examination it is soon found that they most frequently oc- 
cur in groups of one or more pairs, usually in a single group of two, Fig. 1 ; 
but also occasionally in a series of such groups, for example, as in 
Fig, 2, which is a reduced outline of a portion of one of the slabs I have 
inspected. Another frequent group is one of three impressions, arranged 
as in Fig. 3. 
In some instances the markings forming these groups are of the largest 
size yet discovered, — 18 inches long by 10 inches broad. I am inclined to 
think, however, that this particular arrangement of the markings into a 
group of three is merely an example of a double group of two, the fourth 
impression being probably hidden by the overlying rock, or missing from 
some other cause. 
Mr. Taylor, in his account of his discovery of similar fossil footprints at 
Dalby, considers them to have been formed by a tortoise-like chelonian, 
and founds his opinion partly upon the fact that the footmarks he dis- 
covered strongly resembled the Canadian prolichnites figured in Owen's 
' Palaeontology,' and which were, in the first instance, supposed to have 
been formed by a chelonian ; and partly upon the fact, that upon the slab 
in his possession the impressions were " about 4 inches on each side of a 
straight line, alternately on this side and on that." This reference of these 
markings to a chelonian origin is not, I believe, borne out by later researches. 
Professor Owen (quoted by Murchison, ' Siluria,' first edition, page 205), in 
consequence of the discovery of better specimens, now refers them to crusta- 
ceans, an opinion confirmed by the discovery of similar crustacean markings 
by Professor Harkness in Roxburghshire in 1855. " These curious impres- 
sions are not at all unlike those for larger prints which Professor Owen 
has so well described, and which were found by Sir W. E. Logan in the 
Potsdam sandstone of Canada. In this case, however, it would appear 
that a single pair of legs successively produced the imprints (not four, or 
five, or more, as in the Canadian tracks), and they are most likely to have 
been made by an animal swimming with difficulty in very shallow water, 
such as Professor Harkness proves to have been the condition of the lo- 
cality from physical evidence " (' Siluria,' page 168, edition 1859). From 
this it would appear that the original supposition that the " Prolichnites " 
were the tracks of chelonians, has not been borne out by more recent dis- 
coveries, but that they are now referred to a shrimp-like crustacean, analo- 
Impressions iu the Cambrian (?) Slates. 
