FAMILY 38. CHILOSTOMELLIDAE 295 



KEY TO THE GENERA 



I. Test trochoid throughout, three chambers to a whorl Allomorphina. 



II. Test trochoid in the young, later planispiral. 



A. Two chambers in each coil. 



1. Aperture at the side of the test. 



a. Aperture narrow Chilostomella. 



b. Aperture rounded Chilostomelloides. 



2. Aperture terminal Seabrookia. 



B. More than two chambers in each coil. 



1. Chambers high. 



a. Aperture simple, narrow, low Allomorphinella. 



b. Aperture fimbriate Chilostomellina. 



2. Chambers low. 



a. Aperture broad, low, chambers regular Pullenia. 



b. Aperture narrow, semielliptical, chambers irregularly in- 



volute Sphaeroidina. 



Subfamily 1. Allomorphininae 



Test in the adult with usually three chambers to a whorl, the 

 chambers inflated and enlarging rapidly as added; aperture, 

 an elongate, curved slit at the ventral border of the last-formed 

 chamber. 



Genus ALLOMORPHINA Reuss, 1850 



Plate 45, figures 1, 2; plate 46, figure 7 

 Genoholotype, Allomorphina tyigona Reuss 

 Allomorphina Reuss, Denkschr. k. Akad. Wiss. Wien, vol. 1, 1850, p. 380. 



Test trochoid, in the adult with usually three chambers to a 

 coil, the chambers inflated and enlarging rapidly as added, often 

 very involute ; wail calcareous, perforate ; aperture, an elongate, 

 arched opening below the border of the last-formed chamber on 

 the ventral side, sometimes with a slight lip. 



Upper Cretaceous to Recent. 



Subfamily 2. Chilostomellinae 



Test in the adult with two chambers making up a coil, the 

 chambers inflated and enlarging rapidly as added; aperture 

 variously modified, lateral or terminal. 



