470 TRANSACTIONS OF SECTION C. 
Yorkshire differ from the genotype in the fact that the cells are typically 
rounded in cross section and by the absence of perforations in the cell-walls, 
and he therefore proposes to separate it as a new genus Solenoporella. It 
seems probable that some confusion has arisen between the specimens to which 
Nicholson originally gave the name of S. jurassica from the Great Oolite of 
Chedworth and other specimens from Malton from a higher horizon °*—the Coral 
Rag-—examined by Dr. Brown and Professor Rothpletz. 
The former author indeed figures a longitudinal section from Chedworth 
(Glos.) and a tangential section from Malton (Yorkshire), as the same species. 
I have collected specimens from both horizons and consider that the Ched- 
worth specimens, to which the name of Solenopora jurassica was originally given, 
represent a species of true Solenopora, showing closely packed cells with 
polygonal outline in tangential section, the form from the Coral Rag of York- 
shire, with distinct circular outline to the tubes in tangential section, is 
specifically, if not generically distinct, and is that described by Rothpletz as 
Solenoporella. 
If this view be correct we should continue to speak of the specimens from 
the Great Oolite at Chedworth as Solenopora jurassica, while those from the 
Coral Rag of Yorkshire must be known as Solenoporella sp. Rothpletz. 
Foreign Jurassic. 
In foreign Jurassic rocks the recorded occurrences of Calcareous Alge are 
surprisingly few. 
Quite recently, however, Mr. H. Yabe°® has described a new species of 
Solenopora, under the title Metasolenopora Rothpletzi, from the Torinosu lime- 
stone of Japan. This discovery is of interest, as it carries the known occurrence 
of Solenopora up to the base of the Cretaceous, in which formation Titho- 
thamnion appears and thenceforward becomes the chief representative of the 
rock-building Coralline Algz. 
CRETACEOUS. 
We here reach the period when ZLithothamnion and its allies begin to make 
their appearance. They have not yet been recognised in British rocks, but are 
widely distributed in continental deposits. They occur in the Cenomanian of 
France, in the Sarthe and the Var, but especially in the Danian of Petersburg, 
near Maestricht. 
Other forms which may be mentioned are Diplopora and Triploporella. The 
former is met with abundantly in the lower Schrattenkalk in certain districts, 
especially Wildkirchli, where it plays a considerable part in the formation of the 
deposit.*” 
TERTIARY. 
In Britain no example of marine Calcareous Alge have, so far as J am aware, 
yet been reported, but considerable deposits of freshwater limestone, rich in 
remains of the lime-secreting Thallophyte Chara, have for long been known from 
the Oligocene of the Isle of Wight. 
Foreign Tertiary. 
On the Continent, however, thick deposits rich in Lithothamnion and 
Lithophyllum have been known for many years. _ Of these, I may mention 
especially the well-known Leithakalk of the Vienna Basin and Moravia, which it 
will be remembered formed the subject of Unger’s important monograph in 1858.°* 
CONCLUSIONS. 
The facts given above regarding the geological distribution and mode of 
occurrence of these organisms lead us to several interesting conclusions. In the 
6 See Fox Strangways, Geol. Mag., 1894, Dec. IV., vol. I., p. 236. 
6 Op. cit. (©), p. 2. 
67 Arbenz, Vierteljahrschr. Naturf. Ges.-Ziirich, 1908, vol. LIIL., pp. 387-392. 
68 Denksch. k. Akad. Wiss. Miinchen, 1858, vol. XIV., p. 13. 
