W. B. CARPENTER ON THE STRUCTURE OF ORB1TOLITES. 95 



the sarcodic substance is almost liquid, and there is a continual 

 circulation or interchange taking place ; but there is no dif- 

 ferentiation of function that I can find. The Red Sea specimens 

 having two rows of marginal pores, furnish a curious intermediate 

 condition (Fig. 9) ; having a single annular stolon in each ring, but 



Fig. 7. 

 Diagram illustrating the Pedigree of the Complex type of Orbitolite. 



1. Simple undivided spire of Cornuspira. 



2. Partially interrupted spire of Spiroloculina. 



3. Spire of Peneroplis, divided by partitions into chambers. 



4. Spire of Orbiculina, its chambers divided into rows of chamberlets. 



5. Disk of " simple " Orbitolite, showing first-formed spire, surrounded by 

 concentric rings. 



6. Disk of " duplex " Orbitolite, showing earlier passage from spiral to 

 cyclical plan of growth. 



7. Central portion of disk of " complex " Orbitolite, in which the cham- 

 bered nucleus alone shows an abbreviated spire, the very first row of 

 chamberlets forming a complete ring. 



