120 REPOKT— 1871. 



I'tfera, Pallas, sp., may have some of its corallites subdivided by perfect 

 tabula) ; the species of Cijathopliora of the Oolites also ; yet it would be a most 

 objectionable and improper proceeding to remove these genera from their 

 recognized alliances. I found an Astrcvopora in the Museum at Liver- 

 pool with tabula; ; and Mr. Kent has pointed out the perforate affinities of 

 Koninclcia and of the form he has published. Some Eugosse have perfect 

 tabula;, others have them not ; and in Ci/clojjJiyllum and Glisiophyllum dis- 

 sepiments exist in some parts of a corallum and not in others, where they 

 are replaced by tabulae. This interesting fact may be gleaned from James 

 Thomson's sections taken from the Scottish corals. 



JSTevertheless there are forms which are essentially tabulate, and not rugose, 

 but which, so far as their hard and septal structures are concerned, may 

 be aporose in one instance and perforate in another ; for instance, Cohwmaria 

 and Favosites. These forms may still p»'ovisionalhj be considered Tabulata. 



Alliances. — The Lower Cretaceous and Neocomiau corals appear to connect 

 the oldest and the newest faunas, and to form an excellent starting-point 

 both for the study of the Tertiary as well as for the Palasozoic forms. It 

 will be readily observed that the succession of genera and species from the 

 lower Cretaceous horizon to the present day is gradual ; and that although 

 many forms died out, still the general appearance of the consecutive faunas, 

 such as those of the Middle and Upper Cretaceous, the Nummulitic, the Oii- 

 gocene, the Miocene, the Pliocene, and of the two great faunas of the present 

 day, presents a remarkable similarity of Avhat is usually called " facies." 

 The similarity between the Lower Cretaceous fauna and that of the Miocene 

 has been treated of elsewhere *, and the analogies of the mid-tertiary corals 

 and those of the Pacific also. Moreover since the last Eeport was read the 

 distinction between reef, deep-sea, and littoral corals has been more satisfac- 

 torily established, and the reason why consecutive faunas upon the same 

 areas could not possibly be identical, even as regards the genera, has been 

 explained f. 



As the Coral-faunas are studied from those of recent date backwards in 

 time, extinct forms are met with which gradually fill up the spaces in the 

 very natural received classification, and it is perfectly evident that the existing 

 species were foreshadowed in the past. A great number of existing species 

 lived in the so-called Pliocene, and not a few in the Miocene %. Eeuss's 

 admirable researches amongst the vast reefs which are of an intermediate age 

 between the Flysch and the typical coral districts of the Miocene age, have 

 carried back the homotaxis of the existing coral areas to a time which has 

 hardly been recognized by British geologists, but whose fossils are clearly 



cavities in a horizontal plane. In some species the dissepiments are curved, and are as 

 incomplete as ■when they are more or less horizontal in others, and vesicular endotheca 

 exists, more or less, in nearly all the forms. 



There are no true tabula^ and the dissepiments do not interfere in any way with the 

 jiassage of the septa from the lowest part of the corallum to the calice. 

 There are eight species of HdcrophyUia : — 



Heteropbyllia grandis, M'Coy. Heterophyllia M'Coyi, Duncan. 



— — ornata, M'Coy. Lyelli, Duncan. 



■ granulata, Duncan. mirabilis, Duncan. 



angulata, Duncan. Sedgwicki, Duncan. 



The first two are found in the Carboniferous limestone of Derbyshire, and the otliers in 

 the Scottish Carboniferous strata (see Phil. Trans. 1867, p. 043 et seq.). 



* West-Indian Foss. Corals (P. M. Duncan, Quart. Journ. Geol. Soc. sxiv. p. 28). 



t Coral Faunas of Europe (Quart. Journ. Geol. Soc. xxvi. p. 51 ct seq.). 



I Corals of Porcupine Expedition (Proc. Eoyal Society, xviii. p. 289). 



