Mr. H. J. Carter on the Structure of the Foraminifera. 321 



cord ; that vertical branches also, from each turn of the cord 

 opposite the interseptal spaces respectively, keep up a commu- 

 nication (by joining the radiating branches of the different layers 

 of the spiral lamina) between the marginal plexuses of the turns 

 of the cord and the surface ; and that, in some Nummulites, 

 where there is a transverse division in the portions of the cham- 

 bers extending up towards the centre, corresponding with the 

 turns of the spire, the radiating branches are connected by 

 transverse ones ; so that, in fact, each chamber is surrounded by 

 an anastomosing circle of canals thus formed, while, in the re- 

 ticulated Nummulites, this anastomosis becomes retiform from 

 the reticulated division of that part of the chambers which enters 

 into the composition of the spiral lamina. Lastly, the canal- 

 system sends off branches which open on the surface in the 

 course of the interseptal spaces and along the spiral canals, as in 

 Operculina. Thus in each lamina of the Nummulite the canal- 

 system of the horizontal plane is repeated. 



Vertical tubuli. — These enter into the formation of each spiral 

 lamina just as they do into the single one of Operculina. 



Non-tubular spaces. — Such are parts of the test which are not 

 traversed by either the vertical tubes or the branches of the 

 canal-system, and, as before stated, in recent Operculina arc 

 marked by a homogeneous semitransparency of the shell-sub- 

 stance, while in the fossilized species they are opake and white, 

 — a transition which leads to the knowledge of what they are 

 and were in Nummulites. They may be linear, radiating, or 

 sinuous, as when forming that part of the test over the inter- 

 septal spaces, or punctiform, as when in the midst of the vertical 

 tubuli, and in both positions afford signs, according to their 

 form and number, for specific distinction. In N. biaritzensis 

 these white parts may be seen to form also a minute branch- 

 work, which extends perpendicularly outwards from the septal 

 lines ; and in N. perforata a similar branchwork may be observed 

 to spread both from the septal lines and the puncta (very like 

 the lacuna? and their branchwork in bone), but to such an ex- 

 tent in some specimens as to present a minute reticulation all 

 over the cameral spaces, so much resembling a capillary canal- 

 structure, that, at first sight, there seems to be no doubt of it. 

 However, their being formed of an opake-white substance like 

 the septal lines and the puncta first leads to the opinion that 

 they are not tubes ; and this is confirmed by microscopical exa- 

 mination of portions of the spiral lamina of N. perforata pre- 

 senting this structure, when ground down to a thinness sufficient 

 to allow the light to pass through them ; for besides the absence 

 of any double line indicative of the presence of a tube in these 

 white lines (which are then found to be made up of little dis- 



Ann.^ Mag. N. Hist. Ser.3. Vol,\m. 21 



