92 A. EARLAND ON ORBICULINA ADUNCA. 



angles from the parent disc, and occasionally these flanges become 

 so numerous that the original disc can only be traced with 

 diflSieulty. 



In the fourth and final genus of the subfamily, Orbitolites, the 

 arrangement of the chamberlets attains a still more complex 

 form ; but it lies outside the scope of this paper, inasmuch as the 

 crosier form is confined to the earliest stages of certain species 

 only, and the adult shells are all normally discoidal. The desired 

 increase in the area of the oral apertures is also obtained in a 

 difierent manner by means of subsidiary chamberlets, the arrange- 

 ment of which was very fully described by the late Dr. Carpenter. 



