156 THE FOEAMINIFEEA 



Genus Orhitoliini^ D'Oebigny. 



Test conical, more or less depressed, consisting 

 of an external series of annular or more rarely 

 spiral chambers, divided into chamberlets ; also a 

 central aggregation of compressed chamberlets, in 

 which the partitions are either labyrinthic or arranged 

 in tiers. Base of cone usually excavate. Shell-wall 

 fairly stout, and subarenaceous in texture. Lower 

 and Upper Cretaceous. 



A very flat and explanate type of this genus is 

 the Cijclolina cretacea of D'Orbigny. 



Example. — 0. concava, Lamarck sp. 



This is one of the largest species of the genus, 

 often reaching a diameter of 2 centimetres. The 

 external layer of chambers are in this form arranged 

 in an annular series, and the central group of 

 chamberlets are more or less acervuline. Ceno- 

 manian. (Plate 8, figs. J, j.) 



Genus Connlites, Caetee. 



Test conical, usually steep, the height being- 

 greater than the width at the base. The external 

 series commences with a distinct spiral, which either 

 continues to the last coil or subsequently gives place 

 to an annular arrangement. The external chamber- 

 lets, into which the chambers are divided, are 

 separated by straight partitions forming rectangular 

 cells, and the chamberlets themselves are partially 

 divided by one to three short dissepiments. The 

 internal portion of the test is divided into curved 



