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



centre, while they so increase vertically as to become cylindrical, 

 and thus cause the horizontal plane to be much thicker at the 

 circumference than in the centre. The columnar chamber- 

 structure is exactly the same as in Orbitoides, but there are no 

 columns of condensed white shell-substance. Vertical tubuli 

 exist throughout the horizontal layers of shell-substance, as in 

 Nummulites. The canal-system is composed of two sets of sar- 

 codal channels, which permeate the test. The first consists of 

 radiating horizontal ones which spread off spirally, like the lines 

 on an engine-turned watch-case, from the centre to the circum- 

 ference ; these are arranged in layers, commencing with two (?) 

 in the centre, which are separate from each other, but whose 

 lines, crossing in their course to the circumference, after the 

 manner mentioned, unite separately with the chamber which is 

 fixed in the internal angle of the interspaces that they thus form; 

 afterwards they become doubled and trebled as the chamber 

 lengthens, so that at the circumference each chamber becomes 

 connected with six of such canals, and six openings appear be- 

 tween the chambers, at the margin of the test, in zigzag, one 

 above another. The second set consists of annular horizontal 

 canals, arranged concentrically in two layers only, viz. one on 

 each side the horizontal-chamber layer, on a level with the ends 

 and between the rows of chambers respectively with which they 

 are united on the inner side : also a subsystem consisting of 

 much smaller canals, one set of which connects the annular 

 bands horizontally between the chambers; another connects 

 them vertically, through the horizontal plane; and the third, 

 only seen occasionally, seems to ascend vertically from the an- 

 nular canals of each side to be lost in the interspaces between 

 the columnar chambers. Here also one cannot help seeing the 

 sarcodal system of Orhitolites given in Dr. Carpenter's diagram 

 (Phil. Trans. 1856, pi. 5. fig. 6) ; but I do not see that scolloped 

 form of the annular bands in the infiltrated specimens which 

 appears in the uninfiltrated ones (PL XVII. fig. 2 o), and is 

 represented by Dr. Carpenter as bearing the chambers in Or- 

 hitolites ; nor do I see the stolon-process coming from the con- 

 vexities of the scollops to form the chambers of the next row 

 outwards, unless the faint transverse radiating lines of the " sub- 

 system " be these (PI. XVI. fig. 2, 1 2). Further, Dr. Carpenter 

 (p. 222) only allows a single layer of annular bands in the simple 

 type of Orhitolites ; and assuming that the horizontal plane of 

 Orhitolites Mantelli commences in the same way, we might 

 assume that it also possesses only a single layer; but the mi- 

 nuteness of the structure in the central part almost defies this 

 decision in my specimens. 



The reader will now have seen the differences between Orhi- 



