486 



ANNELIDA. 



small comparative width, and easily recognisable from the matrix by 

 their darker colour and slightly different texture. These meandering 

 markings wind over the surface of the stone in indefinite undulations, 

 often appearing to cross one another ; and no one, looking at such 

 a specimen, would be inclined to doubt that he had to deal with 

 the trails left upon the mud of the sea-shore by some soft-bodied 

 marine animals, though he might question if these could be An- 

 n elides. Other specimens, however, of the same fossil, which have 

 been carefully examined by the author, prove conclusively that, in 

 spite of appearances, Myrianites is not only not Annelidan in its 

 nature, but that it cannot possibly be the track of any animal what- 

 ever. It can be shown, in fact, that the narrow serpentine markings 

 upon the surface of the stone, which are universally understood 

 under the name Myrianites, are really the cut edges of thin vertical 

 laminar expansions, sinuously folded, and seen in horizontal section. 

 In fig. 349, c, a portion of one of the specimens referred to is 



Fig- 35°- — CrossoJ>odia Scotica, a supposed Annelide track. Silurian. (After M'Coy.) 



figured, from which it will be seen that the fossil cuts directly across 

 the lamince of deposition, its actual surface (where exposed by exfolia- 

 tion of a part of the slab) being marked with concentric striae. It 

 is therefore quite clear that Myrianites was really a thin, erect, folded, 

 leaf-like expansion, of some kind or another, and that what palaeon- 

 tologists have described under this name is only the horizontally-cut 

 edge of this expansion as seen on the surface of the stratum. What 

 Myrianites really is, is quite an open question. It is, perhaps, a 

 peculiar form of Fucoid. That it is not Annelidan seems perfectly 

 certain. 



Another fossil which has generally been regarded as referable to 

 the Errant Annelides is the Crossopodia of M'Coy (fig. 350), also 



