Mr. H. J. Carter on the Fossil Foraminifera of Scinde. 467 



zigzag form to reach the surface : 1 , column of chambers ; 2, ver- 

 tical tubuli of the test ; 3, tubes of intercommunication between 

 the columnar chambers ; 4, ditto, terminating by open mouths 

 on the surface, thus ultimately enabling all the interior chambers 

 to communicate with the surface. 



g, h, i. Vertical sections of different parts of the horizontal plaue 

 or chamber-layer, to show the various forms of the chambers at 

 these parts respectively. 



g. Portion midway between the centre and circumference, 

 showing — 1, chambers of the horizontal plane ; 2, tubular com- 

 munications between them ; 3, chambers of the columnar struc- 

 ture ; 4, vertical tubuli of the test passing between them ; 5, trun- 

 cated ends of the annular canals ; 6, ascending tubes of inter- 

 communication between the chambers of the horizontal and 

 columnar layers. 



h. Form of chamber near the centre. 



i. Form of chambers in the external rows. 



k. Horizontal section of portion of the horizontal chamber- 

 layer, showing — 1, chambers; 2, tubes of intercommunication; 



3, annular canal above the chamber-layer ; 4, ditto below ditto ; 

 5, transverse canals uniting the annular ones. 



I. More magnified view of a portion of the same, showing — 

 1, chambers; 2, tubes of intercommunication ; 3, annular canals; 



4, transverse canals uniting the annular ones. 



Fig. 2. Orbitolites Mantelli, Cart., magnified twice the size of the specimen. 



a. Portion of the surface magnified, showing — 1, ends of co- 

 lumns of chambers ; 2, shell-substance between them. Observe 

 that there are no columns of condensed shell-substance here. 



b. Vertical section of entire fossil, the lower part not shaded, 

 showing — 1, the horizontal plane or chamber-layer much thicker 

 at the circumference than in the centre, with, 2, the radiated 

 arrangement of the columns of chambers above, and the absence 

 of the opake white columns of condensed shell-substance. This 

 figure has been more or less proportionally magnified, for com- 

 parison with the corresponding figure of Orbitoides dispansa on 

 the other side. 



N.B. Here it should be remembered that the contour of the 

 vertical sections of these fossils respectively only represents that 

 of the specimens from which they are taken, viz. figs. 1 and 2. 

 Either may be compressed almost to flatness, or raised in the 

 thick part to semisphericity. Hence the impossibility of distin- 

 guishing them without reference to their minute structure. 



c. Portion of surface greatly magnified, showing — 1, ends of 

 the columns of chambers ; 2, intercameral shell-substance tra- 

 versed by the tubes of intercommunication between the chambers; 

 3, truncated ends of some of these tubes ascending to the cham- 

 bers of the next layer. The latter of course open on the surface 

 when there is no other layer above them, and thus ultimately 

 enable the chambers to communicate with the exterior. 



d. Vertical section, showing the absence of the opake white 

 column of condensed shell-substance seen in the opposite figure : 

 1, columns of chambers; 2, vertical tubuli between them; 3, in- 

 tervening shell-substance ; 4, tubes of intercommunication be- 

 tween the chambers. 



e. Horizontal section still more magnified, showing — 1, cham- 

 bers laid open ; 2, section through the test, showing the ends of 



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