Nomenclature of the Foraminifera. 37 



the newest or outermost annuli. Bronn, op. cit. p. 86, errs in 

 describing the apertures or pores as being on the edge of the last 

 chamber. The septa of the annular chambers are limbate; but 

 the secondary or cross septa (though probably present) give no 

 evidence of their existence. This absence of limbation of the 

 secondary septa is such as occurs in certain specimens of Or- 

 bitolites. 



Orbitolina discoidea, Gras (Foss. del'Isere, p. 52, pi. 1. f. 7-9), 

 is a thick flat form ; and possibly Orbitolites plana and O. ma- 

 millata, D'Archiac (Mem. Soc. Geol. France, ii. p. 178), may also 

 be Orbitolina of the same character. D'Archiac's Orbitolites 

 media {op. cit. p. 178), placed by D'Archiac and Bronn with 0. 

 Faujasii, is an Orbitoides, as IVOrbigny has indicated. The 

 last, however, mistook O. Faujasii for an Orbitoides. 



D'Orbigny's species O. radiata (Prod. ii. p. 280), from Royan, 

 is not well characterized. There are many radiate and stellate 

 Foraminifers in the Maestricht Chalk and the Nummulitic Ter- 

 tiaries which may be either Orbitolince, Orbitoides, or Calcarince. 

 The radiate ridging of the surface would not be a feature at 

 variance with the growth and habit of Orbitolina. We have not 

 yet, however, sufficient means of comparison to be satisfied as to 

 the relations of the forms referred to, although we believe them 

 to be Calcarinaf. 



With regard to the relationship of Orbitolina to Orbitoides, 

 we may say that they have the same structure, as far as the cell- 

 growth and the interstitial substance* are concerned; but Orbi- 

 toides is always subsymmetrically discoid, or lenticular, heaping 

 cells on both faces of its primary, annular, subdivided chambers ; 

 whilst Orbitolina, which has one symmetrical variety, has many 

 that have no pretence to bilateral symmetry, any more than the 

 conical Rotalice, and, in its typical concavo-convex form, it 

 bears the same relation to Orbitoides that Rotalia does to Num- 

 mulina. The umbilical growth of irregular and imperfect cells 

 in Orbitolina is a feature similar to the astral formation of the 

 divided umbilical lobes of the chambers in some Rotalice (for 

 instance, Asterigerina lobata) ; and we may say that Orbitolina 

 has the same relation to Rotalia that Cycloclypeus has to Num- 

 mulina, — Williamson's Patellina representing Heterostegina. 



The following are the most important varieties of Orbitolina 

 concava, Lam. : — 



1. Orbitolina simplex, P. $• J. Tertiary : Grignon. 



2. semiannularis, P. 4* /• Recent : Indian Ocean. 



* The limbation, arising from septal granulation, of the stellate Orbito- 

 lince from New Zealand and Fiji, and of the conical specimens from Ciply, 

 is not unlike that of some of the Orbitoides of the Maestricht Chalk, 



