THE FORAMINIFERA 139 



(such as those of the Astrorhizidea) which abound in the arctic 

 seas extend, as members of the abyssal fauna, along the ocean 

 floor, to mingle in lower latitudes with the empty tests of the 

 pelagic inhabitants of the warmer surface waters. 



Notwithstanding the wide range of many species, there is some 

 indication of a limitation of forms to definite areas the formation 

 of local faunas comparable to that met with in the distribution of 

 other animals and of plants. Thus in the warm shallow seas 

 of the Malay Archipelago Mr. Millett finds the forms deviate in 

 many instances from the ordinary structure of the Foraminifera. 1 

 In his reports hitherto published, dealing with the orders as far 

 as and including the Lagenidea, he has described twenty-six new 

 species and one new genus from this region. 



Geological Distribution. Representatives of four orders of the 

 Foraminifera Textularidea, Lagenidea, Rotalidea, and Globi- 

 gerinidea have been recognised in the Cambrian, the oldest of the 

 " palaeozoic " formations. In the Carboniferous all the orders are 

 represented except the Miliolidea which have,however, been recog- 

 nised in beds transitional between the Carboniferous and the Per- 

 mian the small and fragile Chilostomellidea, and the Gromiidea, 

 whose slight tests we should hardly expect to find preserved. 

 In the Carboniferous formation species of Saccammina and Fusulina 

 give rise to extensive deposits. An abundant foraminiferal fauna 

 has been found in many of the secondary formations, and the chalk 

 of the later Cretaceous period is in large part built up of their 

 tests, Gloligerina being an abundant form as in the oozes of the 

 existing ocean basins. 



Foraminifera also enter largely into the composition of the 

 earlier rocks of the Tertiary period. The Miliolidea here come 

 into great prominence, and are represented by Miliolina (including 

 Quinqueloculina and Triloculina),a,nd its allies Peneroplis, Orbitolites, and 

 Alveolina. Nummulites, which had already made their appearance 

 in the Carboniferous period, also abounded in the warm shallow 

 Eocene seas, and the Nummulitic limestones extend across the old 

 world from the Pyrenees to China, attaining in some places 

 thousands of feet in thickness. 



It need hardly be pointed out that our knowledge of the life- 

 history of the Foraminifera is still very far from complete. In the 

 establishment of the prevalence throughout the higher groups of 

 the phenomenon of dimorphism, dependent on different modes of 

 reproduction, a substantial groundwork has been attained, but 

 there remain many important questions of wide biological bearing 

 on which we are very imperfectly informed. 



1 Report on the Recent Foraminifera of the Malay Archipelago collected by Mr. A. 

 Durrand, F.R.M.S., Journ. Roy. Microscopical Soc. 1898, p. 258. 



