Mr. H. J. Carter on the Structure of the Foraminifera. 329 



discoidal fossil consists of a horizontal plane of oblong chambers 

 covered in on each side by a mass of columnar ones. The 

 chambers of the horizontal plane arc in circular rows, concentri- 

 cally arranged around a central globular cell, which may be 

 large or small. [Formerly I stated that they began "multi- 

 spirally," and gave a figure (Ann. Nat. Hist. ser. 2. vol. xi. pi. 7, 

 p. 2G) to prove it; but I have since found that this was drawn 

 from a section of a minute Hcterostcgina which I had mistaken 

 for an Orbitoides.~\ Each chamber is connected with the two 

 immediately behind and before it respectively by stolon-pro- 

 cesses; and the chambers generally increase in length in the 

 radial direction of the test with their distance from the centre, 

 up to a certain point, when their vertical diameter preponderates 

 over their horizontal one, not from increase of the former, but 

 from diminution of the latter, following, therefore, the same law 

 that is observed in Nwnmitlitcs. The columnar chambers, on 

 the other hand, are arranged in convex layers arching over the 

 horizontal plane ; each chamber is compressed vertically, varies 

 in shape and size, and is united to those immediately around it 

 by stolon-processes. Interspersed between the columnar cham- 

 bers are a number of columns, of a conical shape, having their 

 pointed ends on the horizontal plane and their large extremities 

 on the surface; these consist of non-tubular condensed shell- 

 substance, which is opake and white in the fossil, and are ana- 

 logous to the white columns in Nummulites and similar struc- 

 tures in recent Operculina. Vertical tubuli exist throughout the 

 horizontal layers of shell-substance, as in Nummidites ; and there 

 is a double horizontal canal-system, consistiug of a single layer 

 of network tubulation on each side of the horizontal plane, whose 

 meshes are parallelograms, and enclose respectively one of the 

 oblong chambers. One cannot help seeing here a part, at least, 

 of the canal-system of Cycloch/peus (Phil. Trans. 1856, pi. 29. 

 fig. 11). Whether it be from the smallness of my specimens 

 (which, however, are T 4 ^ to T 8 ^ inch in diameter) or the smallness 

 of the canal-system (but I think the former, from the remnants of 

 this system being most evident in the largest ones), no other part 

 of the canal-system which has been described by Dr. Carpenter 

 in Cycloclypeus appears to be developed in them. 



Orbitolitcs Mantelli, Cart. (PI. XVI.fig.2, &c.).— This discoidal 

 fossil consists of a horizontal plane of globular chambers, which 

 become cylindrical externally and are covered in on each side by 

 a mass of columnar ones. Those of the horizontal plauc are in 

 circular rows, concentrically arranged around a central one, and 

 are not connected by stolon-process, but attached to sarcodal 

 canals, as will be mentioned directly ; they also increase only 

 slightly in their horizontal diameter with their distance from the 



