802 



here described, no fewer than four are also found in European 

 strata, nainelj in tlie Eocene Clavulina annularis d' Orb. and 

 67. parisiensis d' Orb., in the Miocene SpirolocuUna crenata Karrer^ 

 in the Miocene and Pliocene Gypsina globulus Reusji. This wide- 

 spread horizontal distribution in tiie Tertiary period corresponds to 

 a still wider distribution at the present day, for the mentioned 

 SpirolocuUna and Gi/pshia inhal)it the Atlantic and the Indian and 

 Pacific Oceans; both species of Clavulina occnr in the Atlantic, the 

 former also in the Indian Ocean and the latter in the Pacific. 

 Of the remaining surviving species found in the formation here 

 dealt with, Orbitolite.'i niaryinalis Lamk. occurs again in the three 

 Oceans, while Polystomella craticulata F. e. M. is spread from the 

 Mediterranean through the Indian Ocean to the Pacific and the 

 uncertainly determined Orbiculina adanca F. e. M. is found from 

 the Atlantic as far east as the Philippines. 



Also the vertical distribution of the foraminifera differs from that 

 of the mollusca, as is best seen from the numbers of the surviving 

 species in both groups. Among 103 determined mollusca 7 recent 

 forms are found, among 9 determined foraminifera 6 — 7. Hence the 

 Rhizopoda would make a much younger impression when compared 

 with the mollusca if it were not that also the extinct subgenus 

 Floscalinella was found in it, besides Lepidocyclina and Miogypsina. 



From what precedes it follows: 



1. That the foraminifera mentioned do not alter in the least the 

 Indopacific character of the Neogene Indian fauna, though they may 

 occur outside the Indopacific area and partly in the European tertiary. 



2. That the foraminifera, generally S|>eaking, cannot 

 serve in the same way as the mollusca for determining the age of 

 the strata and that this animal group is also less serviceable for 

 investigations on marine geographj'. 



As to this latter point we may remember here the extraordinarily 

 wide horizontal and vertical distribution of Orbitolites complanata 

 Lamk., whereas the highly developed nuramulinidae have proved 

 eminently suitable for an exact determination of the age of deposits. 



How shall we now explain the difference in distribution observed 

 between mollusca and foraminifera and between the groups of the 

 foraminifera among themselves ? To me it would seem that it is 

 closely related to our conception of a species. The species namely 

 with which one has to deal in palaeontology are no physiological 

 but morphological species. The individuals of such species of mollusca 

 and foraminifera as we are here only concerned Avith, agree in a 

 single anatomical element, the shell. Such an agreement may exist, 



