Mr. H. J. Carter on the Structure of the Foraminifera. 323 



i& a yellow argillaceous limestone, in such a way that, by careful 

 fracture, they fall out with surfaces so polished and even, that 

 their preservation, thus far, may be said to be complete ; and 

 hence the marking on the surfaces respectively is most evident. 

 We, therefore, have only to put the margins of N. Ramondi and 

 this Operculina together, and bring them into the focus of a 

 microsco])ic power, to see that those on the cord of the Operculina 

 are a facsimile of those on the cord of recent Operculina arabica, 

 which we know to indicate a spicular composition, and that 

 those on the cord of N. Ramondi are precisely like those of the 

 fossilized Operculina, with the exception that the lines are less 

 interrupted in the cord of the Nummulite, and are therefore, 

 continuously, much longer, which indicates much longer spi- 

 cules ; but the fact of all the spicules not being of the same form 

 or of the same length in the same species, or of different lengths 

 generally in another most closely allied organism, to wit Num- 

 mulites, does not affect the verity of the spicular composition of 

 the cord. Indeed, writing of these lines as supposed grooves, 

 MM. d'Archiac and Haime state (p. 63), " Les sillons, dont le 

 nombre et le degre de rapprochement varient un peu, sont sen- 

 siblement droits et continus dans la plupart des cas, mais quel- 

 quefois {N. laevigata, pi. 4) ils sont tres legerement flexueux, et 

 assez frequemment interrompus." The latter is the case with 

 the lines on the cord of N. Ramondi ; and the same interruptions 

 or terminations, in a pointed form, I have observed in N. spira. 

 Further, on comparing the cords of the two fossils mentioned, 

 viz. Operculina and N. Ramondi, we observe a number of red 

 points in the lines or intervals between the spicules, which are 

 nothing more than red oxide of iron filling the canals of the 

 marginal plexus in both the Operculina and Nummulite, which 

 open on the surface of the cord. Thus the identity in structure 

 and composition of the surface of the spicular cord in Operculina 

 and Nummulites is so far complete. But we have still the inte- 

 rior to identify, which, as far as the layers (planes of spicules in 

 Opei'culina) radiating from the inner side of the cord to its cir- 

 cumference go, even to their being constricted at intervals into 

 a number of short portions, and the planes of the canal-system 

 between them, I have been able to see in the N. spira, N. sub- 

 len-iyata, and N. Ramondi, both in the transverse and horizontal 

 section of their cords respectively ; still not the remotest trace 

 of the circular or the horizontal lines of the spicules in either the 

 one or the other of these sections have I seen. When, however, 

 it is remembered that, although I have preparations to show 

 distinctly the linear contours of the spicules in the horizontal 

 section of the cord of Operculina arabica, and therefore can 

 infer the existence of the circular lines which they must present 



21* 



