512 



FORAMINIFEKA I NUMMULITES. 



a, a ; whilst the appearance they present when cut across in a 

 Horizontal section is shown in Fig. 259, the transparent Shell 



Fig. 258. 



Portion of a thin Section of Nummulina laevigata, taken in the 

 direction of the preceding, highly magnified to show the minute 

 structure of the Shell:— a, a, portions of the ordinary Shell- 

 substance traversed by parallel Tubuli; b, b, portions forming 

 the Marginal wall, traversed by diverging and larger Tubuli; 

 c, one of the Chambers laid open ; d, d, d, Pillars of solid sub- 

 stance not perforated by tubuli. 



Fig. 259. 



! il§ 



substance a, a, a, being closely dotted with minute punctations 

 which mark their orifices. In that portion of the Shell, however, f 

 which forms the margin of each whorl (Fig. 258, b, b), the tubes 



are larger, and di- 

 verge from each 

 other at greater 

 intervals ; and it is 

 shown byHorizontal 

 sections that they 

 communicate freely 

 with each other 

 laterally, so as to 

 form a network 

 such as is shown at 

 b, b, Fig. 260. At 

 certain other points, 

 d, d, d (Fig. 258), 



.„..,„,. r the Shell-substance 



Portion of Horizontal Section of Nummuhte, • . ~f n ~r>+ a A 



showing the structure of the Walls and of the Septa f 8 no \ penorauea 

 of the Chambers :— a, a, a, portion of the wall by tubes, but IS 

 covering three Chambers, the punctations of which peculiarly dense in 

 are the orifices of Tubuli; 6, b Septa between i ts texture, forming 

 these chambers, containing Canals which send out ,., p.,, ' ,. ? 

 lateral branches, c, c, entering the Chambers by sollcl -t rUars wnicn 

 larger orifices, one of which is seen at d. seem to strengthen 



