36 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 2, 



by the dark spots at the angles of its divisions. These spots are 

 obviously the transverse sections of the passages already described, 

 which are filled with opake matter ; they are much larger in sections 

 taken near the external surface, on account of the infundibuliform 

 shape of these canals. In some instances these passages seem to 

 have been very large and open, especially towards the external surface, 

 as is shown in fig. 10, where they are indicated by the dark spots. 

 But in other instances (as shown in fig. 9, a, a) these spots are di- 

 vided by lines, which seem like delicate partitions dividing the entire 

 canal into smaller passages. This harmonizes well with the idea that 

 each passage might have given exit to a fasciculus of pseudopodia, 

 hke that which we have supposed to issue from the passages in Num- 

 muhte, which bear so close a resemblance to those now under con- 

 sideration. 



After a careful survey of the characters presented by the group of 

 fossils I have been describing, I feel strongly inclined to the conclu- 

 sion that their affinity is rather to the Nummulites than to the Orbi- 

 tolites, and that the animals which formed them are more likely to 

 have been Foraminifera than Bryozoa. I cannot see any strong point 

 of real resemblance between Orbitoides and Orbitolite, the difference 

 in the position of their respective chambered layers being kept in view ; 

 on the other hand, the resemblances between Orbitoides and Num- 

 mulite are very close ; whilst the differences are by no means so great 

 as those which exist among other members of the singular group of 

 Foraminifera, and which seem chiefly to depend upon variations in the 

 mode of gemmation. 



The Foraminiferous character of Orbitoides appears further to be 

 indicated by the presence, in all the species I have examined by 

 sections taken through the centre, of the large globular cavity (fig. 

 35, a), resembling that which is stated by M. D'Orbigny and Mr. 

 Williamson to be the ordinary form of the first segment of the Fora- 

 minifera, whatever may be the form which the compound structure 

 may subsequently present. 



EXPLANATION OF THE FIGURES. (Plates III. to VIII.) 



Fig. 1. Transparent section of Nummulina Icevigata, nearly parallel to the median 

 plane, passing at the upper part through the marginal portion, and at 

 the lower through the central portion, of one of the investing whorls, and 

 showing the irregular form of the perforations, which are here filled 

 by a crystalline infiltration of carbonate of lime. Magnified 10 diam. 



Fig. 2. Transparent section of Nummulina lavigata, through the median plane, 

 showing portions of several successive whorls : at a is seen a sudden en- 

 largement in the size of the chambers ; and at c is seen a narrow whorl 

 intervening between two broader ones, b and d. The chambers are 

 filled by a crystalhne infiltration of carbonate of lime, which, in many 

 of them, has a deep tinge in the centre of the deposit, apparently de- 

 rived from the presence of carbonaceous matter. Magnified 10 diam. 



Fig. 3. Fragment of Nummulina Icevigata obtained by fracture through the median 

 plane, and shovring the manner in which the marginal whorls are con- 

 tinued as investing layers over those previously formed, and in which 

 the marginal septa are prolonged between these layers ; showing also 

 that each septum is composed of two layers vnt\i an intervening space. 

 Magnified 12 diam. 



