PRESIDENTIAL ADDRESS. 469 
Mizzia and Stolleyella—from a dolomite in the Upper Carboniferous of northern 
Dalmatia, while a species of Girvanella (@. sinensis) has been described by 
Yabe *° from the (?) Carboniferous rocks of San-yu-tung and other localities in 
China. 
PERMIAN AND TRIAS. 
In Britain I have met with no reference to the occurrence of Calcareous Algw 
in rocks of this period, but quite recently Mr. Cunnington, of H.M. Geological 
Survey, sent me a few nodules from the base of the ‘ Permian’ near Maxstoke; 
in thin sections they resemble very closely fragments of Spongiostroma from 
the Carboniferous Limestone, and may be derived from that formation. 
Abroad, masses of limestone, composed almost entirely of remains of Diplo- 
pora and Gyroporella, have long been known from the Muschelkalk and lower 
Keuper beds of the Eastern Alps, notably the Mendola Dolomite, the Wetten 
limestone of Bavaria, and the Tyrolian Alps—from the Zugspitz to Berchtes- 
gaden, also from the Hauptdolomit and the Fassa Dolomite of the North lime- 
stone Alps and the stratified Schlern dolomite of the Southern Tyrol. In the 
Lombard Alps the same facies reappears, and Diplopora annulata occurs abun- 
dantly in the well-known Esino limestone above Varenna. 
In 1891 Rothpletz °** showed that certain spherical bodies in the Triassic beds 
of St. Cassian, formerly regarded as oolitic structures, were in reality algal 
growths, and referred them to a new genus, Spherocodium, on account of their 
apparent resemblance to the living form Codium. He describes them as encrust- 
ing organisms forming nodules up to several centimetres in diameter. They 
confribute substantially to the rocks in which they occur, and are found 
especially in the Raiblkalk, the Kossenerkalk, and the Plattenkalk. 
JURASSIC. 
The Mesozoic rocks of Britain contain but few examples of marine algal 
limestones, and important occurrences are confined to the Jurassic Rocks. The 
forms met with are limited to two genera, Girvanella and Solenopora. 
Tubes of Girvanella occur fairly abundantly in the British Oolites, especially 
in the well-known Leckhampton Pisolites, and Mr. Wethered, who has made 
a special study of oolitic structures, appears inclined to refer all oolitic structures 
to organic agency of this nature. 
The examples of Solenopora met with in the Great Oolite*? and Coral Rag 
are of special interest. In both cases they attain very much larger dimensions 
than any species yet discovered in the Paleozoic rocks. 
At Chedworth, near Cirencester, I have collected masses of Solenopora 
jurassica, measuring up to a foot across, in which the original pink tint is still 
so conspicuous on freshly-fractured surfaces as to give rise to the local appel- 
lation of ‘Beetroot Stone,’ and the colour also reminds one of the red alge 
growing in great profusion at the present day in the Gulf of Naples. 
It is also recorded from the same horizon from near Malton in Yorkshire by 
Dr. Brown,® and also, on the authority of the late Mr. Fox Strangways, by 
Professor Rothpletz.** 
In Yorkshire, however, one form undoubtedly occurs at a higher horizon— 
namely, in the Coral Rag of the Scarborough district, where it is well known 
to local collectors. Specimens which I have collected from this horizon at 
Yedmandale and Seamer also attain a considerable size—up to six inches in their 
longest dimension. 
The name Solenopora jurassica was given by Professor Nicholson in manu- 
script to specimens from Chedworth, and was adopted by Dr. Brown in his 
description of the specimens from both Chedworth and Malton in Nicholson’s 
collection. 
Professor Rothpletz points out that specimens examined by him from 
60 H. Yabe, Science Reports of the Téhoku Imp. Univ., Japan, 1912. 
61 Zeitsch. d. deut. Geol. Ges., 1891, vol. XLIII., pp. 295-322, pls. XV.—XVII., 189]. 
® Proc. Cot. Nat. Club. 1890, vol. X., p. 89. 
83 Op. cit. (®), p. 150. & Op. cit. (°). 
