LAURENTIAN AND EARLY PALEOZOIC. 39 



cussed the questions relating to Prototaxites. Drepano- 

 vhycus, of Goeppert,* I suspect, is only a badly preserved 

 branch or stem of the Erian land-plant known as Arthro- 

 tigma. In like manner, Haliserites Dechenianus,\ of 

 Toeppert, is evidently the land-plant known as Psilopfiy- 

 ton. Sphcerococcites dentatus and 8. serra the Fucoides 

 dentatus and serra of Brongniart, from Quebec are 

 graptolites of two species quite common there. J Die- 

 tyophyton and Uphantenia, as described by Hall and the 

 author, are now known to be sponges. They have be- 

 come Dictyospongice. The curious and very ancient fos- 

 sils referred by Forbes to the genus Oldhamia are perhaps 

 still subject to doubt, but are usually regarded as Zo- 

 ophytes, though it is quite possible they may be plants. 

 Though I have not seen the specimens, I have no doubt 

 whatever that the plants, or the greater part of them, 

 from the Silurian of Bohemia, described by Stur as Algse 

 and Characeae,* are really land-plants, some of them of 

 the genus Psilophyton. I may say in this connection 

 that specimens of flattened Psilopliyton and Arthrostiy- 

 ma, in the Upper Silurian and Erian of Gaspe, would 

 probably have been referred to Algae, but for the fact that 

 in some of them the axis of barred vessels is preserved. 



It is not surprising that great difficulties have occurred 

 in the determination of fossil Algas. Enough, however, 

 remains certain to prove that the old Cambrian and Silu- 

 rian seas were tenanted with sea- weeds not very dissimilar 

 from those of the present time. It is further probable 

 that some of the graphitic, carbonaceous, and bituminous 



* "Fossile Flora," 1852, p. 92, Table xli. 

 f Ibid., p. 88, Table ii. 



t Brongniart, " Vegeteaux Fossiles," Plate vi., Figs. 7 to 12. 



* "Proceedings of the Vienna Academy," 1881. Hostinella, of this 

 author, is almost certainly Psilophyton, and his Barrandiana seems to in- 

 clude Arthrostigma, and perhaps leafy branches of Berwynia. These 

 curious plants should be re-examined. 



