POEITES. 3 



eastern side of the Atlantic Ocean, a chain of fossiliferous areas — some of them, e.g. the Paris 

 Basin, the Italian Miocene, the Egyptian Deseit. and Persia, very rich in Poritids — connects 

 the Atlantic with the East. But there seems to be no certainty as to whether these at any 

 time formed actual co-existing links. This matter of co-existence need not be important : it is 

 enough that Tertiary seas have at one time or another opened into one another, making it 

 possible for Poritids to spread from West to East and East to West. Tertiary deposits in Asia, 

 indicate that there may have been water connection between the Mediterranean and the 

 Indian Ocean by way of Persia and the Persian Gulf, and between the Mediterranean and the 

 Pacific across Asia ; while, on the other hand, there is evidence for the belief that the 

 Mediterranean area was at one time in zoological connection across the Atlantic with the West 

 Indies. A study of the Tertiary strata for the purpose of ascertaining tlie conditions of their 

 Poritid faunas is a desideratum. The earliest appearance of the genus Gomo-pora occurs in the 

 lower Cretaceous of the Crimea. It seems to have reached its maximum in the middle 

 Tertiaries. It is possible that Pontes, as a derivative of Goniopora, is attaining its maximum 

 in modern seas. 



This suggestion is based upon the reviews of the family contained in Vols. IV., V., VI. 

 of this Catalogue. It will there be found that the great bulk of the fossil Poritids which have 

 been found in the Tertiary strata, of whicli the records have been referred to by the writer, 

 nearly seventy belong to the older genus Goniopora, while less than ten belong to the genus 

 Porites. 



Unless further research reverses this proportion, its significance for the evolutionary 

 history oi Porites, as a derivative of Goiiiopora, is of weight. In this connection, we may mention 

 that the discovery of fossil Goniopora in Jamaica (though no living form is known to occur 

 in the West Indies to-day) is in harmony with the view that the genus Goniopora has had its 

 day, and has been giving place to Porites. [See Vol. IV., p. 27, and Vol. V., p. 24, for the 

 morphological derivation of the Porites from Goniopora by the suppression of the tertiary septa, 

 not as a gradual process of abortion, but by the early ripening and fixing of immature forms, 

 that is, of early stages which have not yet developed their tertiary septa.] 



II. HISTORICAL. 



A brief sketch of the family Poritidas was given in Vol. IV. p. 4, and of the genus Porites 

 in Vol. V. p. 3. We can, therefore, here confine our attention entirely to a sketch of the work 

 done on the Atlantic and West Indian representatives of the genus. The partial and separate 

 treatment is quite justifiable not only on the grounds of morphology — inasmuch as we shall 

 show in the next section, p. 12, that the forms of this region are a group apart — but also 

 because the story is complete in itself, nowhere overlaps, and is more than ordinarily 

 instructive. It supplies us with an ideal illustration of the futility of trying to build up any 

 solid knowledge of the closer inter-relationships of the forms of life by the help of imaginary 

 units, whether we call those units " species " or " forms." For both of them are imaginary, 



B 2 



