FORAMINIFERA. 105 



evidence of any fundamental modification or advance of the 

 Foraminiferous type from the Palaeozoic period to the pres- 

 ent time." Lastly, the Foraminifera are not altogether reli- 

 able tests as to the depth of water in which the deposits 

 containing them were laid down. As a rule, they abound 

 principally in warm and shallow seas. The " Globigerina 

 ooze " of the deep Atlantic and Pacific occurs mainly at great 

 depths, but though doubtless partly composed of forms which 

 really lived at those depths, it is principally made up of the 

 shells of Foraminifera which live at or near the surface of 

 the sea. The White Chalk the ancient analogue of the 

 Atlantic " ooze " may therefore^ have been laid down in 

 any depth of water, since its prevalent types of Foramin- 

 ifera were probably mainly surface-forms. 



CLASSIFICATION OF THE FORAMINIFERA. The classification 

 of the Foraminifera has proved a matter of considerable dif- 

 ficulty. The older arrangements were unnatural, as being 

 based wholly on the form of the shell, a point in which the 

 Foraminifera show a most marvellous variability. For this 

 reason the artificial systems proposed by D'Orbigny and Max 

 Schultze have now been generally abandoned, and their place 

 has been taken by the schemes of classification put forward 

 independently and almost simultaneously by Professor Von 

 Reuss upon the Continent, and by Dr Carpenter, Mr Parker, 

 and Professor T. Rupert Jones in this country. Both these 

 arrangements agree in the essential feature that they divide 

 the Foraminifera into two great primary divisions, in accord- 

 ance with the nature of the shelly investment. In the one 

 division (Imperforata), the test is not perforated by pseudo- 

 podial apertures, and it may be either " arenaceous " or " por- 

 cellanous." In the other division, the test is perforated by 

 more or less numerous pseudopodial foramina, and to this 

 division the name of Perforata is applied. The following 

 tables exhibit the arrangements proposed by Carpenter, 

 Parker, and Rupert Jones, on the one hand, and Reuss, on 

 the other hand ; the former being the most natural, and the 

 one most widely adopted : 



