alge. 
CRETACEOUS. 
We here reach the period when Lithothamnion 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 Peters- 
burg, near Maestricht. 
Other forms which may be mentioned are Diplopora 
and Triploporella. The former is met with abun- 
_dantly 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 important deposits of marine cal- 
careous algz have yet been reported, but considerable 
deposits of limestone, rich in remains of Chara, have 
_ for long been known from the Oligocene of the Isle 
of Wight. 
Foreign Tertiary. 
On the Continent, however, large deposits rich in 
Lithothamnion and Lithophyllum have been known 
for many years, among which I may mention the 
well-known Leithakalk of the Vienna Basin and 
Moravia. It, will be remembered that it was these 
deposits which formed the subject of Unger’s im- 
portant 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 addi- 
tion to the evidence of the important part they play 
as rock-builders, it is evident that certain forms 
flourished over wide areas at the same geological 
periods, and might well be made use of in many cases 
with considerable reliability as proofs of the general 
contemporaneity of two deposits. Thus, as general 
examples, we may cite the wide distribution of 
Solenopora compacta in the Baltic provinces, Scotland, 
_ England, Wales, and Canada during Llandilo-Caradoc 
times. 
The wonderfully persistent development of the 
_ Rhabdoporella facies over the whole of the Baltic area 
at the close of Ordovician times was of so marked a 
character that by means of boulders scattered over the 
north German plain it can even be made use of for 
tracing the direction of flow of the ice-sheet during 
glacial times. 
Again, to take examples nearer home. The 
Ortonella band found throughout Westmorland and 
north Lancashire near the summit of the Tournaisian 
occurs so constantly at the same horizon as to con- 
stitute one of the most valuable zonal indices in the 
succession of the north-west province, and can be used 
with the greatest confidence not only for correlating 
widely separated exposures, but also affords valuable 
evidence in the case of tectonic movements. Other 
examples are supplied by the ‘“Girvanella nodular 
band” at the base of the Upper Dibunophyllum zone, 
and the Mitcheldeania gregaria beds in the north of 
England and the Forest of Dean. 
_ Again, the presence of these organisms at a par- 
ticular horizon furnish us with interesting evidence 
as to the conditions which obtained during the accu- 
‘mulation of these deposits. 
_ At-the present day calcareous algz flourish best 
_ in clear but shallow water in bays and sheltered 
lagoons. As a good example we may take the algal 
banks in the Bay of Naples, described by Prof. 
33 Lorenz, 1908. 
NO. 2291, VOL. 92] 
chief representative of the rock-building coralline 
NATURE 
L2a 
Walther,** where Lithothamnion and Lithophyllum 
flourish to a depth of from 50-7o metres. There is 
seldom any muddy sediment on these banks, though 
detrital limestone fragments are widely distributed. 
Another interesting point is the constant association 
of fossil calcareous algz with oolitic structure and 
also with dolomite. 
Thus oolites occur in connection with Solenopora 
in the lower Cambrian of the Antarctic, in the Craig- 
head limestone at Tramitchell in the Ordovician rocks 
of Christiania and the Silurian of Gotland and in the 
Lower Carboniferous limestone of Shap; while in the 
Jurassic rocks of Gloucestershire. and Yorkshire it 
occurs in the heart of the most typical oolitic develop- 
ment to be met with in the whole geological succes- 
sion. Though Mr. Wethered has made out a good 
case for the constant association of Girvanella tubes 
with oolitic grains, there are many cases in which 
their association cannot be traced. M. Cayeux,*® in 
writing of a mass of Girvanella from the ferruginous 
oolites of the Silurian rocks of La Ferriére-aux- 
Etangs, expresses his opinion that Girvanella encrusts 
the oolite grains but does not form them, and that it 
is really a perforating alga of a parasitic nature. 
The presence of dolomites in connection with algal 
deposits at different geological horizons appears to 
have taken place under definite physiographical condi- 
tions similar to those which obtain to-day in the 
neighbourhood of coral reef. Such lagoon conditions 
would come into existence either during a period of 
subsidence or elevation, and this is just what we find 
when we examine the periods at which these reefs are 
most persistent. 
Thus the Girvan Ordovician reef occurred during an 
elevation which culminated with the deposition of the 
Benan Conglomerate; the Lower Carboniferous Algal 
band in Westmorland was laid down during the sub- 
sidence which followed the Old Red Sandstone Con- 
tinental period of the Upper Girvanella; modular 
band occurred when the Marine period of the Lower 
Carboniferous was drawing to a close and a general 
elevation was taking place. Similar conclusions could 
be drawn from other periods recorded above did time 
permit. 
In concluding this address, I wish to express the 
hope that however imperfect the account I have given 
of the succession of forms may be, that it will help 
to stimulate an interest in these rock-building algz 
and encourage geological workers in this country to 
turn their attention to a hitherto neglected group of 
forms of great stratigraphical importance, 
UNIVERSITY AND EDUCATIONAL 
INTELLIGENCE. 
Lreps.—Dr. Charles Crowther, formerly lecturer 
in agricultural chemistry, has been appointed pro- 
fessor in that subject, and will have charge of the 
experiments in animal nutrition, which are being 
supported by a grant from the Development Com- 
missioners. 
The Council of the University has granted six 
months’ leave of absence to Prof. Smithells, who is 
leaving England on September 26 to proceed to 
Lahore, where he is to give a course of lectures and 
to assist the Punjab University in other ways in the 
promotion of scientific education and research. 
The position of research chemist to the Joint Com- 
mittee on Ventilation Research of the Institution of 
Gas Engineers and of the University of Leeds has 
34 “* Zeitsch. d. deut. Geol. Ges.” 1885, p. 230, and, ‘‘Abh. d. Kénigl. 
Preuss. Akad. der Wiss,"’ 1910. 
35 Comptes Rendus Acad. de Sct., 1910, P- 359. 
