304 R. F. TOMES ON MADREPORARIA FROM THE LIAS OF 
this paper a list of the Sutton-Stone fossils is given, amended accord- 
ing to Mr. Tate’s own determination of the species. These, as 
decided by him, represent a fauna which is wholly Hettangian. 
In none of the above papers was the evidence afforded by the 
Madreporaria taken into account. That deficiency I now propose 
to make good; but before doing so, I wish to offer some remarks on 
the value of the evidence derived from them. Possessed of no 
powers of locomotion, and being especially impatient of changes of 
surrounding conditions, corals speedily give way to, and are de- 
stroyed by, alterations affecting unfavourably the purity of the sea 
around them, and in which they have flourished. And supposing 
that existing coral islands and atolls, such as those of the Pacific, 
became imbedded in the strata of some future formation, it is ob- 
vious that they could not be of the age of such deposit, but that they 
would be actually contemporary with the surface of the existing sea- 
bottom around them. Unless, therefore, the layer in which they 
were imbedded should be broken up, and, with its enclosed organisms, 
redeposited, such remains as corals should not properly be taken as 
directly indicating the age of the deposit, but rather as pointing to 
the date of an interval between the older formation on which they 
took their growth and the succeeding and overlying stratum in which 
they would be imbedded. Precisely the same thing would occur 
with coral-banks or with species scattered over a sea-bottom, as with 
reei-builders; and it follows as a necessary consequence that corals, 
unless removed from the place of their growth, cannot properly 
represent any thing more than a period during which very little 
deposition took place. Tested by the above considerations, as well as 
by the affinities of the species themselves, to be hereafter mentioned, 
many, though not, perhaps, all of the corals found in the Sutton 
Stone, if not also those of the Brocastle conglomerate, must be as- 
signed to a period antecedent to that at which those beds were 
formed. 
Amongst the genera adopted by Prof. Duncan for the reception 
of Madreporaria from Brocastle and Sutton are some which, in my 
opinion, demand considerable revision, and I have accordingly made 
some changes in their nomenclature. Most of the so-called Astro- 
ceenic from those localities appear to me to appertain to the genus 
Stylastrea of M, de Fromentel. Cyathoceenia of Prot. Duncan 
I regard as identical with the genus Phyllocenia, as applied to a 
St. Cassian coral by Laube, though quite distinct from the Tertiary 
and Cretaceous Phyllocenie. Of course Prof. Duncan’s name must 
be adopted, and, if I am right in my determination, it must hence- 
forth be recognized as a Triassic as well as Liassic genus. Some of 
the Montlivaltte from the South Wales deposits, from which Prof. 
Dunean’s figures were taken, are either so young or so ill preserved 
as to be wholly useless for specific description. Such are Mont- 
livaltia parasitica, M. brevis, and M. Murchisonie. The peculiarity 
observed in the costze of the last-named species is wholly due to the 
state of preservation of the specimen from which the description 
was taken. The supposed cost are, indeed, nothing more than an 
