12 BRITISH FOSSIL CORALS. 



CHAPTER II. 



CORALS OF THE LONDON CLAY. 



The Eocene deposits, known by the name of London Clay, contain various Corals, 



most of which belong to the two subordinate forms predominant among the Polypi of the 



present period, Zoantkaria aporosa and Zoantharia perforata ; but none of these organic 



remains can be considered as appertaining to species now in existence, or even to those 



found in the more recent tertiary formations. The general aspect of this portion of the 



fossil Fauna of England resembles very much that of the Corals imbedded in the 



" Calcaire grossier" of the Parisian basin. Some species, such as Turbinolia sulcata, 



Styloccenia emarciata, Styloccenia monticularia, and Holaraa Parisiensis, are common to 



both these localities ; but most of those found in the Eocene strata of the environs of Paris 



have not been met with in the London Clay, and many of the Corals belonging to these 



last-mentioned deposits have not been discovered elsewhere. Thus the London Clay 



appears not to contain any Milleporidse, Madreporidse, or Lophoserinse, families which have 



various representatives in the Fauna of the Calcaire grossier, and the only Parisian fossil 



Coral referable to the order of Alcyonaria is a Distichopora ; whereas both Pennatulidae 



and Gorgonidse have been met with in the London Clay. At the present period similar 



differences exist at small distances in the same zoological region, and appear to depend 



principally on the depth of the sea and the nature of the bottom ; by analogy we are 



therefore led to suppose that in the Eocene marine Fauna they are only indicative of some 



such local peculiarities. Indeed, most of the Corals of the London Clay belong to Polypi 



nearly allied to species which are now found in very deep water, and seem to be particularly 



organized for living on a loose, muddy, or sandy ground ; whereas many of the fossil 



Corals of the Calcaire grossier resemble those which now inhabit rocky shores, and are 



seen very near the surface of the sea. 



The principal localities from which our London Clay Corals have been obtained are, 

 Haverstock Hill, Highgate and Holloway, near London ; Barton, Sheppy, Bracklesham 

 Bay, on the coast of Sussex, and Alum Bay (Isle of Wight) ; most of the species were 

 found by Mr. Bowerbank, Mr. Frederick Edwards, and Mr. Frederick Dixon, to whom 

 we are indebted for the specimens figured in this Monograph. 



