PLATE XVI. 



( )rbitolites. 



Diam. Page 



Figures 1-G. — Orbitolites covrvplanat a, Lamarck, sp., . . . 218 



Figs. 1-4. Early stages of the shell ; — 1, Primordial 

 chamber ; 2, 3, very young specimens growing 

 adherent to algfe ; 4, young shell, . x 30 



Fig. ft. Mature specimen ; a, lateral aspect ; b, peri- 

 pheral aspect, . . . . x 20 



Fig. 6. Transverse section of the shell, . x 20 



,, 7. — Orbitolites duplex, Carpenter, . . . x 11 216 



Specimen with waved or slightly sinuate margin. 



,, 8-11. — Orbitolites complanata, var. laciniata, Brady, . . 220 



Figs. 8, 9. Lateral aspect, . . . Natural size. 



Fig. 10. a, Lateral aspect ; h, peripheral aspect, . x 3 



Fig. 11. Transverse section of a portion of the 

 shell, the outer annulii ncompletely parti- 

 tioned, . . . . x 12 



