592 DE. CAEPEXTEE'S EESEAECHES ON THE FOBAMINIFEBA. 



Fig. 3. Section of T. l&vis in the direction of the axis of the cone ; showing at a the 

 spherical primordial chamber, and at b and c the chambers first connected 

 with it on either side ; showing also the manner in which the successively- 

 formed chambers are piled upon one another vertically, with the large lateral 

 orifices of communication between the adjacent chambers. Magnified 50 

 diameters. 



Fig. 4. Ideal representation of a portion of T. Iwvis, to show the relations of the cham- 

 bers, which are divided from one another horizontally by cribriform floors, 

 and laterally by walls in which there are large apertures a, a, a, leading into 

 the adjacent chambers. 



Fig. 5. Section of the basal portion of one of the radiating outgrowths of T. bacu- 

 latus (Plate XVIII. fig. 6), showing the manner in which the chambers are 

 clustered around the solid axis, and in which the axis (a portion of the sup- 

 plemental skeleton) is traversed by canals radiating from its centre to its cir- 

 cumference. Magnified 50 diameters. 



Fig. 6. Section of the Philippine variety of T. baculatus (Plate XVIII. fig. 7), taken 

 through its median plane, showing the mode in which the intermediate 

 skeleton is interposed among the chambers, so as to constitute the axis of the 

 radiating outgrowths. Magnified 25 diameters. 



Fig. 7. Section of T. baculatus, taken in the direction perpendicular to its median plane ; 

 showing an arrangement of its chambers essentially corresponding to that 

 exhibited on a larger scale in fig. 3 ; the piles of chambers partially separated, 

 however, from each other by the interposition of the solid columns of the 

 ' intermediate skeleton.' Magnified 40 diameters. 



Fig. 8. Portion of a section of T. baculatus, taken (as fig. 2) parallel to the median 

 plane, but near the surface ; showing the greater thickness of the walls of the 

 chambers, and the interposition of the solid columns transversely divided at a. 

 Magnified 50 diameters. 



Fig. 9. Portion of a section of the Philippine variety of T. baculatus, more enlarged, to 

 show the canal-system, b, b, traversing the thick walls of the chambers. 

 Magnified 100 diameters. 



Fig. 10. Portion of the section represented in fig. 6, more enlarged, showing, at a, a, a 

 portion of the solid axis of one of the radiating outgrowths, traversed by the 

 canals, b, b, and invested by two layers of chambers, the walls of which are 

 rendered hispid by spinous excrescences. Magnified 100 diameters. 



Fig. 11. Section of the central portion of a specimen of T. baculatus, passing through 

 the median plane ; showing at a its regularly spiral commencement (not 

 distinguishable from that of a Calcarina], the origin of the spines from the 

 intermediate skeleton of the spire, and the early exchange of the spiral type 

 for an irregular clustering of the chambers, as shoAvn at b. Magnified 80 

 diameters. 



