494 Prof. Garwood — Calcareous Algoi. 



of Girvan. Speaking of these beds Nicholson & Etheridge remark : 

 "At this locality S. compacta not only occurs as detached specimens 

 of all sizes, but it also makes up almost entire beds of limestone ; 

 indeed, some of the bauds of limestone at Saak look like amygdaloidal 

 lavas, while others have a cellular appearance from the dissolution 

 out of them of the little pea-like skeletons of this fossil." ' 



In Professor Nicholson's collection from these beds Dr. Brown * 

 afterwards distinguished two new species, namely, S. nigra and 

 !S. dendriformis. Thus, in the Ordovician rocks of Esthonia, Soleno- 

 pora plays quite as important a part (as a rock-forming organism) as 

 it does in the Girvan district in Ayrshire. 



In Norway, again, in the Mjosen district to the north of Christiania, 

 Solenopora occurs plentifully in Stage 5 of Kiser's^ Ordovician series. 

 Here it is very abundant and often builds entire beds, while, further 

 east, at Furnberg, Kieer again records the occurrence of abundant 

 nodules of Solenopora compacta, var. Peachii. 



In addition to Suloiopora, however, examples of another important 

 group of Calcareous Algas, the Siphoneae, occur in great abundance 

 in the Ordovician rocks of the Ealtic region, where they play a part 

 in the formation of calcareous rocks scarcely less important than 

 that played by Gyroporella and Biplopora in the rocks of the 

 Alpine Trias. 



The chief forms belong to the family of the Dasycladacese, which 

 is represented in our present seas by the recent genus Neomeris ; 

 they include the genera PalceoporeUa, Basyporella, Rhahdoporella, 

 Vermiporella, Cyclocriyius, and Apidium. These algal limestones 

 represent the horizons from the Jewe Limestone to the Borckholm 

 Beds inclusive. They were originally investigated by Dr. E. Stolley,* 

 who described their occurrence in the numerous boulders which 

 are strewn over the North German plain in Schleswig-Holstein, 

 Pomerania, Mecklenburg, and Mark - Brandenberg. The facts 

 appear to show that during the deposition of the Jewe and 

 the overlying Wesenberg and Lyckholm Limestones an algal facies 

 obtained which extended from Oeland to Estland, and as far north 

 as the Gulf of Bothnia. But even this area does not represent the 

 full extent of the algal limestone facies in the North of Europe 

 in Upper Ordovician times. In Norway, Kiser^ has shown by his 

 detailed work in the Upper Ordovician rocks (Stage 5) of the Christiania 

 district, the important part played by the Dasycladaceoe in this area. 

 Here the Gastropod limestone in places forms a ' phytozoan limestone ', 

 made up of Rhahdoporella, Vermiporella, and Apidium, associated 

 with a considerable development of oolite. 



Again, at Kuven and Valle, in the Bergen district, Reusch * and 



1 Geol. Mag., Dec. Ill, Vol. II, p. 534, 1885. 



2 Geol. Mag., Dec. IV, Vol. I, p. 145 et seqq., 1894. 



2 " Faunistische Uebersicht d. Et. 5" : Vid. Selsk. Skr., 1897, No. 3. 



* Schr. d. naturw. ver. f. Schleswig-Holstein, Bd. xi, 1897, and references 

 there given. 



* Etage 5 i. Asker. Norges Geol. undersogeles Aarbog, 1902, No. 1. 



^ SUurfossiler og pressede Eo7i glomerate, 1882. " B(j)mmel<t>en og Karm<t>en " : 

 Med. omgiveleser, 1888. 



