442 Mr. H. J. Carter on the 



stance of the fossilized test ; while the whole, in the Sindian 

 species as well as in the Alabama fossil, is covered in by a 

 thin superficial layer of still more compressed cells, which 

 are in juxtaposition, and in lieu of being " circular " are so 

 irregular in outline that altogether they present a reticulated 

 appearance (' Annals,' /. c. pi. vii. fig. 40, a, b), simulating a 

 similar layer in the surface of NuvimuUtes Icevigatus from the 

 Bracklesham beds in England. 



Hence it will have been seen that the central plane in 

 Orhitoides papyracea is composed of " chambers," and that 

 these chambers are rectangular in form ; whereas in Nummu- 

 lites MantelH it is composed of cells, and these cells circular 

 or spheroidal in form (1 call them " cells " because they are 

 spheroidal in form and not rectangular) : the former arranged 

 in rows radiating centrifugally from the centre (' Annals,' 

 /. c. pi. vii. fig. 26), and the latter circularly in the interstices 

 of crossing lines also radiating from the centre, but in oppo- 

 site directions, so as to intersect each other obliquely and thus 

 present the " engine-turned " pattern to which I have alluded. 

 Moreover, that in Orhitoides pajnjracea there are the conical 

 columns of opaque, white, non-tubular shell-substance, and 

 that in Nummidites MantelU there are none. Further, that 

 there is on the surface of the Sindian species a cortical portion 

 possessing a reticulated structure, which is concealed in the 

 Alabama fossil under a smooth structureless surface, and that 

 in Orhitoides papyracea there is nothing of the kind. 



Thus I was led in 1853 to adopt the name of Orhitolites 

 MantelU for Morton's Nummulites ManteUi^ more especially 

 because it appeared to me that this compound structure was 

 but an evolutionary development of the more simple one of 

 Orhitolites marginalis of Lamarck. 



But to understand this more clearly it is desirable that 

 Orhitolites marginalis (which is not only widely spread 

 throughout the warmer regions of the earth, but also typical 

 of the fossilized species, which at least date as far back as 

 the Nummulitic series) should be particularly described. 

 Thus, in general form it is circular, wavy, and concave on 

 both sides, owing to the smallness of the central or first- 

 formed cells and their increasing in size and number of layers 

 towards the circumference. The largest specimens of the 

 recent species that I possess are 5-12ths of an inch in dia- 

 meter and were obtained from the Gulf of Suez, while the 

 largest fossilized specimen that has come under my notice is 

 from the Nummulitic series on the south-east coast of 

 Arabia, and this measures 1 inch in diameter and about 

 l-12th of an inch in thickness (Geol. Papers of Western 



