262 THE FOEAMINIFEEA 



relationship to Vaginulijia, and which D'Orbigny de- 

 scribed under the quasi-generic name of Planularia. 

 The tiny discoidal Ammodisciis, so common in the 

 Carboniferous System, is found profusely in some 

 Liassic clays ; and a related form, though distinct in 

 internal structure, Involutina, here makes its first 

 appearance, and continues nearly to the top of the 

 Oolitic series (Portlandian), where it finally dis- 

 appears, or perhaps gives rise to the more specialised 

 OrhitolincE of subarenaceous structure, which make 

 their appearance in Neocomian strata (0. lenticularis 

 and 0. discoiclea). Certain of the porcellanous forms, 

 as Sinroloculina (often arenaceous also) and Miliolina, 

 are met with in some abundance in the Lias. The 

 hyaline genera are represented by Nodosaria, Mar- 

 ginuUna, Cristellaria (of which the planulate forms are 

 much in evidence), and Folijinorpliina ; the rotalines 

 chiefly being TruncatuUna and Pulvinulina. 



In the Oolitic period the Foraminifera were some- 

 what similar in character to those of the Lias, but 

 show a considerable increase in the number of genera 

 and species, whilst towards the top of the series the 

 fauna shows a certain likeness to those of the 

 Neocomian and Cretaceous strata. Our knowledge 

 of the Foraminifera from the Jurassic system of 

 Germany and France is due to the indefatigable 

 labours of Terquem, whilst Wisniowski and Uhlig 

 have described Polish and Eussian deposits contain- 

 ing Foraminifera. The Jurassic strata of England 

 have not, perhaps, received so much attention as they 

 deserve, but Brady and others have done some work 



