504 Notices of Memoirs — Arctic and Atlantic Basins. 



The tuberculated impressions known as Phymato derma and Cauler- 

 pites may, as Zeiller has shown, be made by the burrowing of the mole- 

 cricket, and fine examples occurring in the Clinton formation of 

 Canada are probably the work of Crustacea. It is probable, however, that 

 some of the later forms referred to these genera are really Algae related 

 to Caulerpa, or even branches of Conifers of the genus Brachyphyllum. 



Nereites and Planulites are tracks and burrows of worms, with or 

 without marks of setse, and some of the markings referred to Palceo- 

 chorda, Palceophycus, and Scolithus have their places here. Many 

 examples highly illustrative of the manner of formation of these im- 

 pressions are afforded by Canadian rocks. 



Branching forms referred to Licrophycus of Billings, and some of 

 those referred to Buthotrepkis, Hall, as well as radiating markings 

 referable to Scotolithus, Gyrophyllites, and Aster ophy cm, are explained 

 by the branching burrows of worms illustrated by Nathorst and the 

 author. Astropolithon, of the Canadian Cambrian, seems to be some- 

 thing organic, but of what nature is uncertain. 



Rhabdichnites and Eophyton belong to impressions explicable by the 

 trails of drifting seaweeds, the tail-markings of Crustacea, and the ruts 

 ploughed by bivalve molluscs. 



Bendrophycus, Bictyolites, some species of Belesserites, Aristophycus, 

 and other branching and frond-like forms, were shown to be referable 

 to rill-marks, of which many fine forms occurs in the Carboniferous of 

 Nova Scotia, and also on the recent mud-flats of the Bay of Fundy. 



The genus Spirophyton, properly so called, is certainly of vegetable 

 origin, but many markings of water action, fin-marks, etc., have been 

 confounded with these so-called ' Cauda-galli fucoids.' 



On the other hand, some species of Palceophycus, Buthotrepkis and 

 Sphenothallus were shown to be true Algse, by their forms and the 

 evidence of organic matter, and Btaliserites, Barrandeina, and Nemato- 

 plxycus were shown to include plants of much higher organization than 

 the Algse. With reference to the latter, it was held that the form to 

 which the name Prototaxites had been given was really a land plant 

 growing on the borders of the sea, and producing seeds fitted for 

 flotation. On the other hand, certain forms to which he had given the 

 name Nematoxylon were allied to Algse in their structure, and may have 

 been of aquatic habit ; very perfectly preserved specimens of these last 

 had been recently found, and had thrown new light on their structure. 



The author proposed to apply to all these problematical plants, 

 having a tissue of vertical and horizontal tubes, the general name 

 Nematophytece or Nematophyton. 



The paper referred to the history of opinion on these objects and the 

 bibliography of the subject; but this, as well as detailed descriptions, 

 are omitted in this abstract. 



II. — On the Belations oe the Geology of the Arctic and Atlantic 

 Basins. By Sir J. William Dawson, LL.D., F.B.S. 



THE paper relates to the evidence of the specimens brought from the 

 Arctic seas bearing on the existence of an ancient line of Lauren- 

 tian Huronian, and other Pre- Cambrian rocks; of the extension of the 

 marine fauna of the Atlantic and the American continental plateau 



