110 J. F. WHITEAVES ON SOME SUPPOSED 
there are met with the remains of a coniferous tree described by Dr. Dawson under the 
name Prototaxites Logani. About 600 feet still higher among these strata, several surfaces 
in succession are marked by serpentining impressions, about an inch wide, deeply grooved 
into the stone, marked by small parallel transverse furrows, which are about a quarter of 
an inch apart. These are perhaps worm tracks and are associated with a few bivalve shells 
of the genus Rensselæria, perhaps R. ovoides.” 
To this description the following particulars may be added: The impressions or tracks 
are invariably imperfect at each end, but the longest continuous one would be nearly four 
feet in length, if straightened out. The width varies in different parts of the same indi- 
vidual, in consequence of the inequalities of the surface of the rock, but it does not appear 
that one extremity is wider than the other. The tracks (if tracks they are) curve in almost 
every direction and hence suggest the idea that the organisms by which they were pro- 
duced were totally devoid of anything approaching to rigidity. Thus one specimen is 
deeply curved in two directions, so that the outline produced is like that of the central 
portion of a snake when in motion, while another forms a single, flexuous loop with the 
two ends crossed. In every case the impressions or tracks are quite simple and shew no 
indications of their having proceeded from anything of the nature of a root, nor do they 
ever bear or throw off lateral branches or branchlets, though the frequency with which 
they cross and recross each other is remarkable. No vestiges can be detected of a longitu- 
dinal central furrow like that of Crossopodia, nor of any lateral appendages like those of 
Phyllodocites or Nereites. The transverse grooves are by no means always equidistant, 
though this appearance may be really due to the accidental obliteration of some of them, 
the matrix being very coarse. These cross grooves also, are not quite parallel, nor are they 
placed exactly at a right angle to the main axis of each impression, but their direction is, no 
doubt, much affected by the frequent and abrupt flexures of the tracks themselves. 
In some respects these supposed tracks bear a certain general resemblance to impres- 
sions made by stems of large crinoids. The Trenton limestone near Ottawa city has yielded 
crinoidal columns, specimens of which may be seen in the Museum of the Geological Survey, 
which are nearly four feet in length, though their breadth is less than halfan inch. But the 
stems of crinoids, although flexible to a considerable extent, yet possess a definite and 
appreciable amount of rigidity, and their transverse annulations are rectangular, equi- 
distant, parallel and very regularly disposed. Moreover, the late Mr. E. Billings, who in 
his lifetime was justly regarded as one of the best authorities on the crinoids of the 
older rocks, and who probably either wrote or endorsed the description of these tracks 
already quoted from the “Geology of Canada,” does not even suggest this as a possible 
explanation. 
The mould or reverse of the Arthrophycus Harlani of the Medina Sandstone would ‘also 
almost certainly present some characters in common with the tracks or markings now 
under consideration. The former fossil, which was first described by Conrad in 1838 as 
Fucoides Harlani, is the type and only species known of Hall’s genus Arthrophycus, which 
is thus defined in the second volume of the Paleontology of New York, published in 
1852: “Stems simple or branehing, rounded or subangular, flexuous, ascending, trans- 
versely marked by ridges or articulations.” To this diagnosis the following comments 
are added: “The species of this genus yet known consist either of simple elongated 
stems of nearly equal dimensions throughout, or of those which divide near the root into 
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