114 
NATURE 
rocks of this country (if we except Rothpietz’s sub- 
genus Solenoporella) is Chara from the Wealden beds 
of Sussex, the uppermost Jurassic of the Isle of Wight 
and Swanage, and the Oligocene of the Isle of Wight. 
Outside of this country the literature on fossil cal- 
careous algz is much more extensive. The interest 
originally aroused on the Continent by the writings of 
Phillipi, of Unger of Vienna, Cohn, Rosanoff, Gimbel, 
Saporta, and Munier-Chalmas has been further main- 
tained in our own time by Bornemann, Steinmann, 
Frith, Solms-Laubach, Rothpletz, Walther, Kiaer, and 
others; while the more favourable conditions which 
obtained for the growth of these organisms, especially 
during Silurian, Triassic, and Tertiary times, has 
afforded a much wider field for their observation. 
Thus, in addition to the forms recorded from this 
country, an important part has been played by mem- 
bers of the family of the Dasycladacez, together with 
such genera as Spherocodium, Lithothamnion, and 
Lithophyllum. 
It is now time to turn to the consideration of the 
_part played by these organisms in the formation of 
the sedimentary rocks through the successive geological 
periods. 
ARCHZEAN. 
In the Archzan rocks no undoubted remains of 
Algze have, so far as I am aware, yet been recorded, 
but Sederholm considers that certain small nodules in 
the Archzean schists of Finland may represent vege- 
table remains. I may also perhaps here refer to some 
curious oolitic structures which I met with in Spits- 
bergen in 1896 when examining the rocks of Hornsund 
Bay. These oolites occur on the south side of the 
bay, and are closely connected with massive siliceous 
rocks which may represent old quartzites. The whole 
series is much altered, and detailed structure cannot 
now be made out. The rocks occur apparently strati- 
graphically below the massif of the Hornsund Tind, 
and may belong either to the Archzean or the base 
of the Heckla Hook series. As, however, similar 
rocks have not been recorded from the type district 
of Heckla Hook, they may be referred provisionally 
to the Algonkian, and may represent the quartzites 
and earthy limestone of the Jotnian series of Scan- 
dinavia. They are mentioned here in connection with 
Mr. Wethered’s view that oolites are essentially asso- 
ciated with the growth of Girvanella. 
CAMBRIAN. 
Passing on to the Palaeozoic rocks, we find in the 
Cambrian deposits very few indications that cal- 
careous algz played any considerable part in their 
formation. 
This is no doubt due, in part, to the conditions 
under which these deposits accumulated in the classical 
localities where true calcareous deposits are typically 
absent. In the Durness limestone, however, where 
considerable masses of dolomites occur, the conditions 
would appear at first sight to have been more suitable 
for the growth of these organisms; but even here the 
slow rate of accumulation and the large amount of 
contemporaneous solution may have militated against 
their preservation. At the same time, it is possible 
that a systematic search in the calcareous facies of 
the Cambrian rocks in the north of Europe and 
America might result in the discovery of the remains 
of some members of this group. That there is ground 
for this suggestion is shown by the recent work in 
the Antarctic continent. 
Prof. Edgworth David and Mr. Priestly have dis- 
covered among the rocks in the north-west side of 
the Beardmore Glacier dark grey and pinkish-grey 
limestone containing the remains of Archzocyathine, 
Trilobites, and sponge spicules, together with abundant 
NO. 2291, VOL. 92| 
[SEPTEMBER 25, 1913 
remains of a small calcareous alga referred provi- 
sionally to Solenopora; from the photographs ex- 
hibited by Prof. David on the oc@asion of his address 
to the Geological Society I have little doubt that this 
reference is correct. 
A further occurrence is also reported from fragments 
of a limestone breccia collected by the Southern party 
from the western lateral moraine of the same glacier. 
Speaking of the fauna discovered in this limestone, 
Prof. David remarks: ‘‘The whole assemblage is 
so closely analogous with that found in the Lower 
Cambrian of South Australia as te leave no doubt as 
to the geological age of the limestones from which 
these fragments are derived."""* This discovery, 
therefore, extends the vertical range of this widely 
spread genus down to the oldest Palzozoic rocks. It 
is interesting to note that the rocks in which the 
Solenopora occurs contain a development of pisolite 
and oolite, and that this is also the case in the 
Australian equivalents. In 1887 and again in 1891 
Bornemann described and figured species of Siphonema 
and Confervites ** from the Archzeocyathus limestones 
of Sardina. As regards the former genus, it was 
shown by Dr. Hinde’* to be congeneric with Gir- 
vanella (Nich and Eth). It is of interest, however, 
to note that Bornemann describes this form as a cal- 
careous alga, and compares it with existing sub-aerial 
algz growing on the surface of limestone rocks in 
Switzerland. The latter is stated by Seward to be 
possibly ‘‘a Cambrian algz, but the figures and 
descriptions do not afford by any means convincing 
evidence.” 
More recently, in 1904, Dr. T. Lorenz has described 
remains of Siphoneze from the Cambrian rocks of 
Tschang-duang in Northern China, for which he 
erects two new genera, Ascosoma and Mitscherlichia, 
placing them in a new family, the Ascosomacez. 
These algz build -important beds of limestone, the 
individuals often attaining a length of 4 cm. and a 
thickness of 13 cm. In 1907 Bailey reported Gir- 
vanella associated with oolites in the lowest Cambrian 
Man-t’o beds in China. It is probable, therefore, 
that as our knowledge of these rocks is extended 
calcareous alge will be found to play an important 
part in the Cambrian limestones of the Asiatic con- 
tinent and Australia. ; 
ORDOVICIAN. 
In the Ordovician rocks, the remains of caleareous 
algze become much more abundant. They are very 
widely distributed, and for the first time they become 
important rock-builders. In Britain, the chief genera 
met with are Girvanella and Solenopora. These two 
organisms occur abundantly in the Scottish Ordo- 
vician rocks of the Girvan area, where they appear to 
have contributed largely to the limestones of the Barr 
series in Llandeilo-Caradoc times. 
As already mentioned, the genotype of Girvanella— 
G. problematica—was originally described by the late 
Prof. Nicholson and Mr. Etheridge, jun., from the 
Craighead limestone, where it occurs in great numbers 
in the Craighead limestone at Tramitchell. The 
officers of the Geological Survey also report it from 
the Stinchar limestone of Benan Hill. 
It occurs in the form of small rounded or irregular 
nodules, varying in diameter from less than a milli- 
metre to more than a centimetre—many of the 
nodules showing marked concentric structure. Dur- 
ing a recent visit to Girvan I was much struck by the 
important part played by this organism in the forma- 
tion of these upper compact limestones In Benan 
Burn, where these beds are admirably exposed, the 
11 Eleventh Inter. Congress Report, 1070, Pp. 775. 
12 “Nova. Acta. Coes. T.eon. Car.,” 1887 and 1891. 
1% Hinde, ‘“‘ Geol. Mag.,” 1887, p. 226. e 
