488 NATURE OF SUPPOSED FOSSIL TRACKS. 



crustaceans, by whose feet tlie indentations are commonly supposed 

 to have been made, were " wholly distinct from the crustacean forms 

 of later geological periods or of the present day." Even apart from 

 sori, the air-bladders in many algse, as I have often proved, are 

 capable of making very distinct impressions on moist sand. 



If the impressions be fucoidal, the otherwise remarkable character 

 of these lateral pit-marks, in differing in number and grouping in 

 different impressions, becomes easily explained without the necessity 

 of having recourse to imaginary specific distinctions. In the impres- 

 sions in which they do not appear, it may be inferred that the fucoid 

 had already scattered its spores, or that the development of the latter 

 had not taken place, when the frond was cast upon the ripple-marked , 

 shore of the old Potsdam sea. 



The supposed fucoidal origin of these impressions would not, I 

 confess however, have been thus advanced, were it not for their asso- 

 ciation or connection in at least one locality — the vicinity of Perth, 

 in Eastern Ontario — with impressions of an analogous character to 

 which an animal origin can scarcely be atttibuted on any rational 

 grounds. These are the impressions known as Climactichnites. It is 

 probable that the supposed animal origin of these latter impressions 

 would never have been conceived, but for their general relations to 

 the Protichnites impressions. The two, it was seen, must evidently 

 have had an analogous origin ; but in view of the peculiar character 

 of the Climactichnites impressions, the aid of some unknown mollusk 

 was called in to explain their formation, although by some observers 

 they have been looked upon as the trails of Trilobites. They may 

 be described, generally, as being in the form of a band of several feet 

 in length, although clearly fragmentary, with a width of from five to 

 six inches. In their general dimensions they agree, therefore, veiy 

 closely with the Protichnites impressions. But they differ from the 

 latter in being traversed transversely by a ser'ies of narrow parallel 

 ridges, about an inch and three-quarters apart, and by having a kind 

 of beaded edge or border — the impression, as remarked by Sir William 

 Logan, thus somewhat resembling a rope-ladder, whence the name 

 Climactichnites. In some examples there is also a central groove or 

 ridge running roughly parallel with the length of the impression. 



The points here to which attention should be chiefly directed are, 

 first, the presence of these numerous transverse ridges ; secondly, 

 their constancy, and the uniform clearness of their outline, throughoui 



