from Southern Nigeria. 203 



Orbitoid (associated with an occasional small s[)ecies of 

 Operculina), which, from microscopical examination, may he 

 referred to the genus OrtUopJiraginina of Munier-Chalmas 

 as interpreted by Schlumberger. 



The i'oraminiferal group of the Orbitoides has been studied 

 by numerous authors for some years, altliough the chief 

 systematic woik on the subject was that accomplished by 

 Giimbel* in 1868, containing important results obtained 

 from an examination of material collected in the northern 

 Alps of Eocene age^ or what was termed " der Kressen- 

 berger Nummulitenschichten." He subdivided the genus 

 Orbitoides of Orbigny into five subgenera — DiscocycUna, 

 Rldpidocyclina, Aktinocyclina, Asterocyclina, and Lepido- 

 cyclina — most of which were founded upon external form or 

 peculiarities of ornamentation. 



In 1896 Verbeek and Fennema f, in their 'Geology of 

 Java,' published researches on the Orbitoides from the rocks 

 of that country, limiting Giimbel's divisions to two instead 

 of five, viz. DiscocycUna (embracing Rhipidocyclina, Aktino- 

 cyclina, and Asterocyclina) for forms with rectangular 

 cliambers in the median plane ; and Lepidocyclina for species 

 having rounded chambers in the median plane. Such results 

 were based entirely on internal structures, and in this way 

 differed from that of Giimbel. From the horizonal point of 

 view their work was of immense value, because they found 

 that the species of DiscocycUna^ at any rate in the Indian 

 Archipelago, belonged entirely to Eocene and Oligocene 

 rocks, whilst forms of Lepidocyclina never occurred in older 

 deposits than Miocene, and apparently became extinct in 

 Pliocene times. The geological views expressed by these 

 authors are now generally acknowledged to apply equally 

 well to the distribution of Orbitoidal organisms in the 

 European formations. 



During 189D the present writer, in conjunction with 

 Mr. Richard Holland |, wrote an account of some 'J'ertiary 

 Foraminifera from Borneo, with special remarks on the 

 Orbitoides, and adopted the views of Veibeek and Fennema 

 in connexion with their studies of those forms. 



Coming more directly to the genus we have to consider, it 

 should be mentioned that Orthophragmina was a name given 

 to certain foraminiferal bodies by Munier-Chalmas § which 



* Abhandl. math.-phys. CI. k.-bav. Ak. Wiss. 1868, vol. x. part '> 

 p. 109. ' "' 



t ' Descript. Geol. de Java et Maduura,' 1896, 2 vols., text and plates. 



X Aun. & Mag. Nat. Hist. 1899, ser. 7, vol. iii. pis. ix. & x. pp. 245-264 



§ "Etude du Tithonique, du Crdtac^ et du Tertiaire du Vicentin," 

 These de Docteur es Sci. Nat. [Paris] 1891, p. 18. 



