456 Mr. H. J. Carter on the Fossil Foraminifera of Scinde, 



and ITaime (p. 350) as being perhaps Orbitoides Fortisi is the 

 fossil from which I have made out the structure above given, the 

 only difference between it and Orbitolites Mantelli being that the 

 columns of cells terminate at the convex part or periphery in 

 polygonal instead of circular cells, — a difference which is hardly 

 enough to make it more than a variety, as the cells are anything 

 but circular in the assumed typical form. 



Associates of Orbitolites Mantelli. — Heterostegina and Cyclo- 

 clypeus, in white limestone at the village of Takah, on the south- 

 east coast of Arabia ; Nummulites suhltEvigata, in yellow argilla- 

 ceous limestone, in Scinde. (This is the specimen to which I 

 have just alluded as being but a variety of Orbitolites Mantelli^ 

 and from which the structural description above given was taken. 

 It is imbedded with the richly infiltrated mass of Nummulites, 

 from which the diagram of Nummulitic structure given in the 

 plate accompanying my description of the structure of Operculina 

 arabica was compiled.) 



Obs. — I have never found Orbitolites Mantelli with any other 

 Nummulite than N. sublavigata, and this only in the specimen 

 above mentioned from Scinde, although it is very common in 

 Scinde. 



Like Orbitoides dispansa, it is sometimes small and prominent 

 in the centre, at others more or less flat, twisted, and expanded, 

 like the ephippial varieties of O. dispansa. The latter, from the 

 wavy and fragmentary state in which it occurs in the matrix, led 

 me into the conjectural error of stating that it sometimes seems 

 to spi'cad itself out in a thalloid form, like the Polyzoa, whereas 

 subsequent examination tends to the conclusion that it always 

 assumes a discoid form, although much more expanded and 

 thinner in some instances than in others*. 



* Since the above v/as written I have had the opportunity of further 

 confirming the opinion I have given, that the expanded forms of OrbitoUtes 

 Mantelli, Cart., are never indefinitely thalloid like the polypidom of the 

 Polyzoa, but always discoid, in a mass of these fossils sent to me by Dr. 

 Cook, which he obtained from a small series of limestone strata overlying 

 serpentine and diorite rock close to the village of Nal, in Beloochistaa, 

 about eighty miles S.S.W. of Kelat. 



This mass, which is a specimen of the stratum from which it was taken, 

 ip so foliated in structure, that it looks like a deposit of leaves ; but when 

 examined, it is found to consist of nothing but Orbitolites Mantelli, Hetero- 

 stegina, Cycloclypeus, and Orbiculina, all together and lying jjarallelly upon 

 each other, in a softish yellow marl. 



The lai'gest specimen of 0. Mantelli forwarded to me is iJJ inches in 

 diameter, } inch thick in the centre, and the central prominence or vertical 

 development not more than i inch wide ; while the horizontal portion, ex- 

 tending 1 inch beyond this all round, is not more than j^ inch thick half- 

 way between the margin and the centre, and increases but a very little 

 more even uj) to the vertical development. It is this small vertical 

 and great horizontal development, which led me formerly, when I had 



