tf2 FOSSIL MEDUS.E. 



1. Against the first he urges the multiplicity of the stria?, their clear- 

 ness, their strictly rectilinear direction, but more especially the fact that 

 they not only touch but intermingle in such a way that one passes above or 

 beneath the other: this he claims could not occur with simple tracks. 



2. Against their being trails made by medusa?, or alga? being dragged 

 over the surface, he adduces the facts that they extend in so many different 

 directions, are so clear, and are often in the shape of veritable cylinders. It 

 is, further, incomprehensible that the Cambrian should have the monopoly 

 of such effects. Lastly, the objection offered in the former case, that the 

 trails intermingle, holds good here. 



3. On the supposition that these are plant remains, all the above facts 

 are perfectly natural. The striae, he says, are not nerves, but superficial 

 longitudinal ridges, not without analogy in Bilobites and Taonurus. He 

 thinks that the markings may be both trails and impressions, the well- 

 defined and solid ones being impressions, the others trails of fragments swept 

 about on the sea bottom. 



In reply to Nathorst, that these never occur with vegetable remains, 

 Saporta describes Eophyton bleicheri n. s. from the environs of Vailhan, 

 which agrees with Eophyton in every way, yet shows dark discoloration 

 due to plant substance. 1 



In an earlier paper Messrs. Saporta and Marion said: 2 



It appears impossible to admit Xathorst's explanation aud not to recognize in 

 the remains described by Torell a vegetable organism similar to others passed in 

 review, though different in genus, yet beyond doubt belonging to the same family. 

 There are shreds, detached fragments, preserved in demirelief and occupying the under 

 surface of Silurian slabs in the greatest disorder. Some of these tatters are flat, 

 ribbon like, others have a cylindrical form, often appearing lacerate; all having their 

 surface furrowed by numerous longitudinal stria?, parallel and regularly disposed. 

 Chance alone could not have produced a similar arrangement, no more than the relief 

 visible in certain of the fragments. 



Whether Dr. Nathorst is correct in interpreting Eophyton as made up 

 of trails produced on fine sand or mud by medusa? may possibly be open 

 to question; but it is true, as he states, that such forms occur from the 

 Cambrian to the Trias, and to my mind it is quite probable that in some 

 instances they may have originated as he suggests. As regards others, 



1 A propos des algues fossiles, Paris, 1882, p. 63. 

 2 L'fivolution (lu ri-gne vegetal; Cryptogames, 1881. p. 83. 



