1869. | DUNCAN—CORAL FAUNAS OF WESTERN EUROPE. 59 
analogies of their structures and specific affinities) either to the 
deep-sea or to the reef fauna. When the fossils are evidently not 
derived from older strata, and not rolled or drifted, their having 
once lived on the area of their fossilization must be conceded. 
Ifthe general arrangement and grouping of forms peculiar to the 
reefs of the existing seas is evidently to be traced in those of the 
Mid-tertiary age, it is logical to admit that the very definite phy- 
sical conditions peculiar to modern reefs existed formerly. This 
general arrangement may be instanced in the vast coral strata of the 
Nummulitic age; and the reefs of that period cannot be distinguished 
by the shape of the species from the coral remains of the Gosau reef 
area, or those of the Neocomian and the Oolites. 
Still earlier in the world’s history, the nature of the coral faunas 
may be estimated by scantily dispersed specimens which possess the 
peculiarities of one or other of the types. 
The relation of high land, older strata, and intrusive rocks, their 
drainage, vegetation, and fauna to coral reefs may be learned in most 
works on physical geography and on the principles of geology* ; and 
there isa possibility, which depends upon the imagination of the geo- 
logist, of forming ideal landscapes whenever corals abound in strata. 
VIII. Genera or Rezr-Faunas, Ancient anp Moprrn. 
The following is a List of Genera whose species form the existing 
and also composed some of the Tertiary and Mesozoic reefs. 
Euphyliia. Diploria. Astrea. Porites. 
Barysmilia. Leptoria. Prionastrza. Alveopora. 
Pectinia. Ceeloria. Agaricia. Pocillopora. 
Galaxea. Hydnophora. Pachyseris. Millepora. 
Stephanoceenia. Favia. Mycedium. Heliopora. 
Symphyllia. Heliastreea. Madrepora. Cycloseris. 
Mycetophyllia. Brachyphyllia. Turbinaria. Trochoseris. 
Ulophyllia. Cyphastrzea. . Astreeopora. Lithophyliia. 
Meeandrina. Solenastrzea. 
Many of the genera are allied to other fossil forms with which 
they were associated ; and by comparing and enumerating the extinct 
genera which lived with those whose species still exist, an extended 
list of reef-makers can be obtained. Such genera as Pachygyra, 
Rhipidogyra, <Astrocema, Phyllocena, Calamophyllia, Rhabdo- 
phyla, Montlivaltia, Thecosmiha, Cladophyllia, Latimeandra, and 
Thamnastrea were associated with many of those in the list given 
above in the reefs of the Miocene, the Nummulitic, the Lower Chalk, 
the Neocomian, and the Oolitic periods. 
The genera characteristic of the deep sea, and whose species do 
not form reefs, may be very well represented by the following list :— 
the genera of the families Turbinolides, Oculinides, many Trocho- 
smiliacez, Lithophylliacez simplices, Cladocoraceer, Kupsammiacee, 
and some Fungiaceze. 
IX. Coraz-sra Conpirions IN DIFFERENT PERIODS. 
The following is a list of the geological periods, showing the rela- 
* Lyell; Dana; Jukes, 
