GONIOPORA. 31 



No recent forms are known from the Mediterranean or Atlantic. On the other hand, it 

 is found fossilised all over the South European area and on through Egypt, Persia, and Northern 

 India. Its presence in the West Indian strata (Antigua) is doubtful (see p. 153). It was 

 especially richly developed in Austro-Hungary, in the region of the Venetian Alps, on the 

 shores of the Atlantic near Bordeaux, and in the Paris Basin. In this last area it developed 

 a great number of small delicate forms, which had a character of their own, not encountered 

 again in any of the living forms. A summary of the records justifies the provisional suggestion 

 that the genus arose in the Lower Cretaceous of the Crimea and then spread, on the one hand 

 over Southern and Western Europe, and on the other through Egypt and Persia into the Indo- 

 Pacific region where alone it still survives. This suggestion has no other scientific value than 

 as a working hypothesis. 



VI. (b) DISTRIBUTION IN TIME. 



The oldest known fossil representative of this genus is from the Lower Cretaceous of the 

 Crimea. It occurs also in the Upper Cretaceous of Bohemia. Other finds which were 

 thought to be of the same period are now regarded as possibly intermediate between Secondary 

 and Tertiary (cf. G. Sind 1, p. 93). The great bulk of the known e.x;tinct forms range 

 from the Lower to the Upper Eocene when the genus flourished all over the seas of Southern 

 Eujope. Through the Miocene it dwindles away. Between that time and the present we have 

 only tivo records (see Table II. p. 168). It is doubtful whether the genus is as plentiful 

 anywhere to-day as it was in Southern Europe during the Eocene period. Apart from such 

 specialised groups as that found in the Paris Basin (usually called Zitharcea), the genus has 

 undergone no striking change. It is possible that there may now be more forms with taU thin 

 walls than before, but tliis (if the main points contained in Sec. III. are correct) is a secondary 

 specialisation. All discussions of this kind are, however, rendered unsafe owing to the facts 

 that fossils so frequently have no original surfaces preserved and that most of the recent repre- 

 sentatives of the genus known to us are shaUow-water forms. There is certainly a wealth of 

 forms both from deeper water and from unexplored strata ; until we have some knowledge of 

 these we are but feeling our way. 



VII. ON THE METHOD ADOPTED OF ARRANGING THE SPECIMENS. 



In writing on this genus, Dr. Ortmann mentions the difficulty he experienced in dividing 

 them into " species " owing to the paucity of characters, the chief being " the size and depth of 

 the calicles," and these he found varied in every specimen. The description of the skeleton 

 here given (Sec. III.) based upon examination of the fine collection in the British Museum, 

 shows a considerable number of new and hitherto unknown characters, but the difficulty of 

 dividing them into genetic groups is not removed. 



The aim of aU comprehensive systematic work should be to try and build up a natural 

 system. The first requisite is to analyse the known forms in order that the primitive form 

 from which they can be deduced can be approximately described. There can be no natural 

 classification without this as a starting point. So far I feel some confidence in having 



