ORBITOIDES. 



637 



FIG. 339. 



presented in Faujasina, as already described ( 291). These 

 canals are frequently found to be filled up in JSTummulites by the 

 fossilizing material ; but a care- 

 ful examination will generally 

 disclose traces of them in the 

 middle of the partitions that 

 divide the chambers (Fig. 339, 

 b, b)^ while from these may be 

 seen to proceed the lateral 

 branches (c, c) which, after bur- 

 rowing (so to speak) in the walls 

 of the chambers, enter them by 

 large orifices (d). As the gene- 

 ral distribution of this system of 

 canals in the Nummulite is the 

 same as that shown in Faujasina 

 (Fig. 209), and as the canals, 

 although smaller, are far more 

 numerous, it is obvious that 

 through its means the segments 

 of sarcode occupying the cham- 

 bers of the most internal walls 

 could send their pseudopodial extensions at once to the exterior. 

 Of all Foraminifera, the Nummulite is undoubtedly one of the 

 most highly developed types ; and its 

 extraordinary multiplication at the 

 earliest part of the Tertiary period, 

 is a very curious feature in the Earth's 

 history. It is commonly considered 

 that this type is now extinct ; but the 

 Author, in common with Prof. Wil- 

 liamson, is disposed to question whe- 

 ther there is any essential difference 

 between Nummulites and the existing 

 genus Nonionina, which is very abun- 

 dant in certain localities; since in 

 many species of Nummulites, as in 

 ISTonionina, the investing layers of the 

 successive whorls are in immediate 

 contact with those that have preceded 

 them, instead of being separated, as 

 in Fig. 337, by spaces prolonged from 

 the cavities of the chambers. 



449. The same Nummulitie lime- 

 stone also contains, in certain locali- Seclion of oroides Prattu, parallel to 



, , ,, -r- , the surface ; traversing at a, a, the super- 



tieS (aS the SOUthwest OI _b ranee, north- fic j a l layer, and at 6,6, the median layer. 



eastern India, &c.) a vast abundance 



of discoidal bodies termed Orbitoides, which are so similar to 



Nummulites as to have been taken for them, but which, while 



Portion of Horizontal Section of Num- 

 mulite, showing the structure of the walls 

 and of the septa of the chambers: a, a, a, 

 portion of the wall covering three chambers, 

 the punctations of which are the orifice's of 

 tubuli ; b, 6, septa between these chambers, 

 containing canals which send out lateral 

 branches, c, c, entering the chambers by 

 larger orifices, one of which is seen at d. 



FlG. 340. 



