ON THE BRITISH FOSSIL CORALS. 103 
This is the earliest species of the genus which has been found in this 
country ; but Septastrwa Fromenteli, Terquem et Piette, which belongs to the 
zone of A. planorbis of the west, has been found in the zone of A. angulatus 
in the east of England. It may have flourished in the zone of A. planorbis 
in the west, and evidently existed contemporaneously with Septastrea Haimezt. 
These are the earliest forms of the genus, which has many Isastreean charac- 
ters, which has its corallite walls rather imperfectly united, and which is re- 
produced by ova and by fissiparity. It is evidently related to a genus of St.- 
Cassian corals which, although not found in the zone of Ammonites planorbis 
in this country, is represented by two species (one a St.-Cassian type) in the 
zone of Ammonites angulatus, in Glamorganshire, The genus is Hlysastrea, 
Laube, which will be noticed presently. 
Septastrewe are not found in Great Britain later than the Lias ; but species 
occur in the French Oolites and in the Miocene. The genus is extinct. 
It was always an assemblage of variable forms, and the irregular septal 
arrangement of the species was the rule. This will be observed from the 
study of the following Table. 
Zesviar Variable ee a 
Byes species. =P 
arrangement. arrangement. 
: Septastraea Haimei......... 1 1 
Hrliost...... —— De Fromenteli ...... 1 1 
A. anculatus { —— De Fromenteli ...... aie 1 1 
eas —— excayata ............+- 1 Be Ee 
A. Bucklandi Hyeshami ............ 1 1 
Oe explanata ........,... aoe 1 
Pahtic. ...... { —— dispar..............000- oe 1 
Miocene...... IHONDOSI, 25 os bapecesnss 1 fer 
There are thus three genera of corals represented in the British zone of 
Ammonites planorbis :— 
Thecosmilia Terquemi, Duncan. Septastrea Haimei, Wright, sp. 
Tsastrxa latimzxandroidea, Duncan. 
And by inference those genera were in existence during the deposition of the 
sediments of the zone which lived in St.-Cassian times, and in the age of the 
zone of Ammonites anqulatus—such genera, for instance, as Montlivaltia, 
Llysastrea, Astrocenia, Rhabdophyllia. 
The zone of Ammonites planorbis is very distinctly developed in France and 
in Luxembourg, and it succeeds without any White Lias intervening upon 
the beds with Avicula contorta. In England the zone is but feebly developed, 
and the upper part of the White Lias cannot be separated from it. The 
separation of the zones of Ammonites planorbis (or its equivalent) and A. an- 
gulatus is satisfactorily determined on the continent, but it is not to be arbi- 
trarily asserted for Great Britain; and in both cases large percentages of 
species are common to the upper and lower zone. 
Triassic fish pass upwards into the zone of Ammonites angulatus in the 
French area, and Triassic Madreporaria are found in the corresponding zone 
in Glamorganshire. Avicula contorta and an Astroccenian are common to the 
Azzarola beds, the Avicula-contorta zone of Great Britain, and the zone of 
A. angulatus. The French zones of the Lower Lias contain Azzarolan 
species. It must be conceded that the White Lias was deposited during the 
age of A. planorbis or A. Burgundie of the French area, the deposits being 
contemporaneous in a general sense—that the Azzarola deposit of Lombardy 
