Ixxx PROCEEDINGS OF THE GEOLOGICAL SOCIETY, [vol. lxxix,, 



floor of the Weddell Sea in lat. 62° 10' S. and believed to be of 

 Cambrian age. The same generic type was discovered by Sir T. W. 

 Edgeworth David and R. Priestley associated with Archceocyathus 

 on the Beardmore Glacier moraines. Epipliyton is, in all proba- 

 bility, an alga comparable in its unseptate branched tubules to the 

 genus Spluerocodium, which ranges from Silurian to Triassic times ; 

 but its precise position cannot be determined. In Solenopora, 

 first described from Ordovician beds in Esthonia, we have the most 

 satisfactory representative among the older algae of a true calca- 

 reous type. Although no undoubted reproductive cells have been 

 found, the structure of the plant-body, as Dr. A. Brown first demon- 

 strated, agrees closely with that of the recent genus Litliothamnion. 

 Detailed descriptions have been published by Prof. Garwood and 

 other authors : I will confine myself to a brief reference to its 

 range in time and its possible relationship to more modern forms. 

 As one of the oldest fossil plants exhibiting internal cellular 

 structure, in contrast to Gryptozoon and the supposed algae 

 described by Dr. Walcott from Upper Archaean rocks in which 

 there is no direct evidence of any organic construction, Solenopora 

 is of especial interest. The genus Lithotli amnion, a member of 

 the Bed Calcareous Algae, with which Solenopora is believed to be 

 closely allied, flourishes both in the tropics and in the Polar 

 regions. It is noteworthy that Solenopora was widespread in Lower 

 Palaeozoic seas, and lived also in the Jurassic Period ; while LitJio- 

 thamnion is met with in the more recent Cretaceous and Tertiary 

 strata. We have here one of many examples furnished by the 

 palaeobotanical record of the persistence of a certain type of organi- 

 zation through a long succession of geological ages. Persistence 

 of t3 r pe, and from time to time the apparently sudden influx of new 

 types, rather than a steady progressive development, are among 

 the outstanding features of the history of plant-evolution. 



The genus NematopTiycus, though perhaps better known as a 

 Devonian plant, occurs also in Silurian rocks ; N. liichsi Daw- 

 son was discovered in the Denbighshire Grits, and N. storriei 

 Barber in the Wenlock Limestone. Originally named by Dawson 

 Prototaocites, the Canadian Devonian species was described by 

 W. Carruthers as a ' colossal seaweed ' under the name Nemato- 

 phycus, for which Dawson substituted Nematophyton. The 

 type-species N. logani Dawson, from the Devonian of Gaspe, 

 is represented by long pieces of stem between 2 and 3 feet in. 

 diameter ; but, as a rule, the specimens are much smaller. 



