PRESIDENTIAL ADDRESS. 461 
the Upper Caradoc or Borckholm beds of Schmidt’s classification—where it 
makes up thick beds of limestone—and it is noteworthy that this horizon is 
practically identical with that at which 8. lithothamnioides (Brown) occurs at 
Shalloch Mill. 
Other specimens of Svlenopora were collected by Professor Nicholson in 
Saak, south of Reval, from the underlying Jewe beds, an horizon which must 
correspond very closely to that of the Craighead Limestone of Girvan. Speaking 
of these beds, Nicholson and Etheridge remark: ‘At this locality 8S. compacta 
not only occurs as detached specimens of all sizes, but it also makes up almost 
entire beds of limestone, indeed, some of the bands of limestone at Saak look 
like amygdaloidal lavas, while others have a cellulac 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, Solenopora 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 Mjésen district to the north of Christiania, Soleno- 
pora occurs plentifully in Stage 5 of Kiaer’s°’ Ordovician series. Here it is very 
abundant and often builds entire beds, while, further east, at Furnberg, Kiaer 
again records the occurrence of abundant nodules uf Solenopora compacta, var. 
Peachii, 
In addition to Solenopora, however, examples of another important group 
of Calcareous Algz, the Siphonez, occur in great abundance in the Ordovician 
rocks of the Baltic region, where they play a part in the formation of cal- 
careous rocks, scarcely less important than that played by Gyroporella and 
Diplopora in the rocks of the Alpine Trias. 
The chief forms belong to the family of the Dasycladacee, which is repre- 
sented in our present seas by the recent genus Neomeris; they include the genera 
Paleoporella, Dasyporella, Rhabdoporella, Vermiporella, Cyclocrinus, and 
Apidium. These algal limestones represent the horizons from the Jewe Lime- 
stone to the Borckholm beds inclusive. They were originally investigated by 
Dr. EK. 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. Many of these boulders can be identified 
by their lithological character and fossil contents as belonging to the Jewe 
beds of the Baltic Ordovician formations. Others have been derived from 
the overlying Wesenberg limestones, while yet others occur which resemble 
the Lyckholm beds of the Baltic succession. This assemblage proves that the 
boulders did not originate on the Swedish continent, but from the more easterly- 
lying districts, probably from a part of the Baltic between Oeland and Estland, 
now covered by the sea. Similar boulders are also known at Lund in Scheenen, 
on Bornholm, and near Wisby in the North of Gotland. 
These 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 this algal limestone 
facies in the North of Europe in Upper Ordovician times. In Norway, Kiaer ** 
has shown by his detailed work in the Upper Ordovician rocks, Stage 5 of the 
Christiania district, the important part played by the Dasycladacee in this area. 
Here the Gastropod limestone in places forms a ‘ phytozoan limestone,’ made up 
of Rhabdoporella, Vermiporella, and Apidium associated with a considerable 
development of oolite. 
Again at Kuven and Valle, in the Bergen district, Reusch *° and Kolderup *! 
have described knolls of crystalline limestone containing abundant remains of 
2 Op. cit. (*), p. 534. 28 Op. cit. (6). 
27 Faunistische Uebersicht d. Et. 5. Vid.-Selsk. Skr. 1877, No. 3. 
8 Schr. d. naturw. Ver. f. Schleswig Holstein Bd. XI. 1897, and references there given. 
9 Etage 5%. Asker. Norges Geol. Undersogeles Aarbog, 1902, No. i. 
30 Silurfossiler og pressede Konglomerater 1882 and Bommelgen og Karn. ben. Med. 
omgivelser 1888. 
51 Ht orienterende niveau Bergensskiferne. Rhabdoporellenkalk von Kuven und 
Valle. Bergens Museums Aarbog, 1897. 
