The Quarterly journal of the Geological Society of London . think, best be interpreted byreference to the smaller and more perfect one. But with this helpthey enable us to observe some characters not plainly visible on No. 1 shows three uiidulating lines of imprints, neither parallel * Quart. Journ. Greol. Soc. vol. xii. p. 100. t A fine slab of markings, probably due to Cephalaspjs, exists, or did exist afew years back, in the great Jerrayn Street Collection. It is from the Cornstonebeds of the OJd Red. A still finer one is in the Worcester Museum, 1867.] SALTER—TRACKS OF PTERASPIS. 33
The Quarterly journal of the Geological Society of London . think, best be interpreted byreference to the smaller and more perfect one. But with this helpthey enable us to observe some characters not plainly visible on No. 1 shows three uiidulating lines of imprints, neither parallel * Quart. Journ. Greol. Soc. vol. xii. p. 100. t A fine slab of markings, probably due to Cephalaspjs, exists, or did exist afew years back, in the great Jerrayn Street Collection. It is from the Cornstonebeds of the OJd Red. A still finer one is in the Worcester Museum, 1867.] SALTER—TRACKS OF PTERASPIS. 335 nor equidistant, nor alike in their depth or direction; nor is thenumber of imprints the same in each track. So that we are at oncerelieved of the supposition that a single individual with three seriesof appendages could have left this as its compound track; and weare at liberty to treat each as independent, though their main direc-tion is the same—namely, along the line of the tide-wash, as indi-cated by the stripe A to A*, B to B*, &c. rig. Two of these, at least, are the track of the same creatuie, repeatedin its double journey from water to shore or vice versa; and I think(but am not sure) the third track is e\idence of another advance ofthe same individual in a parallel direction. We may suppose, then,the effort of the animal (whatever it was) to reach the deeper water 336 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [JuHO 19, from the shore, twice obstructed by the forward wash of the surf,which stranded it again. The tracks A and B are exactly similar,except that one is deeper than the other, and the imprints are atunequal distances ; and they have every appearance of being madeby the same individual. But the difference in depth of the threetracks shows clearly the direction to have been from A to A*, or thereverse; and it will be observed that this line of direction is trans-verse, but a little oblique also, to that of the linear imprints them-selves. The more confu
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