front Southern Xu/erla. 20'^ 



Orl>it«>id (associated with an occasional small species of 

 Opercnlina), wliicli, from microscopical examination, may be 

 ri'tVrred to the genus Orl/ioplinii/minri of ^lunier-Clialmas 

 as interpreted hy SelihMnberj2;er. 



The foraminiteral group of the Orhitoides has been studied 

 by numerous authors for some years, altliongh the chief 

 s\-stematic woik on the subject was that accomplished by 

 (iuml)el* in 1S68, 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 

 OrhitoiJes of Orbigny into five subgenera — Discocyciina, 

 Jiliipidoci/cli'ia, Aktlnocydina, Asterocyclina, and Lepido- 

 cycluta — most of which were founded upon external form or 

 peculiarities of ornamentation. 



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

 Java,' published researches on the Orbitoides from the rocks 

 of that cour.try, limiting GUmbel's divisions to two instead 

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

 cyc/ina, and A.sterocycluia) for forms with rectangular 

 chambers in the median plane ; ar.d 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 CJiinibel. From the Iioi'izonal point of 

 view their work was of immense value, because they found 

 that the species of Discocyciina, 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 oi-ganisnis in the 

 European formations. 



During ]89y the present writer, in conjunction with 

 Mr. Kichard Holland J, wrote an account of some Tertiary 

 Foraminifera from Borneo, with special remaiks on the 

 Orbitoides, and adopted the views of Verbeek 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 Ortkopkragmina was a name given 

 to certain foraminiteral bodies by 3lunier-Chalmas § which 



* Abhandl. ruath.-phvs. CI. k.-bav. Ak. Wiss. 18(58, vol. x. part 2, 

 p. 109. 



t ' Desciipt. G(§ol. de Java et Madoura," 1896, 2 vols., text and plates. 



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



§ "Etude du Tithonique, du CrtStace et du Tertiaire du Vicentin," 

 These de Docteur es >?ci. Nat. [Paris' 1891, p. 18. 



