FAMILY 21. ORBITOLINIDAE 179 



KEY TO THE GENERA 



I. Test high conical, not divided into chambers Howchinia. 



II. Test conical, divided into chambers, aperture not cribrate. 



A. Chambers not labyrinthic Tetrataxis. 



B. Chambers labyrinthic but without distinct chamberlets. . .Ruditaxis. 



C. Chambers labyrinthic, two rows of chamberlets in each chamber. 



Valvulinella. 



III. Test conical-chambered, aperture cribrate. 



A. Mostly siliceous, lower side usually concave. 



1. Apertures on the ventral side OrbUolina. 



2. Apertures on the periphery Cyclolina. 



B. Mostly calcareous, lower side flat or convex. 



1. Without pillars. 



a. Exterior with a finely reticulate structure with two sets 



of outer chamberlets Dictyoconus. 



b. Exterior with a finely reticulate structure, with a single 



set of outer chamberlets Cushmania. 



c. Exterior without a finely reticulate structure, partitions 



between chamberlets double Chapmania. 



2. With pillars Dictyoconoides. 



Genus HOWCHINIA Cushman, 1927 

 Plate 23, figures 1-4 



Genoholotype, Patellina bradyana Howchin 



Howchinia CusHMAN, Contr. Cushman Lab. Foram. Res., vol. 3, 1927, 



p. 42. 

 Patellina Howchin (not Williamson), Journ. Roy. Micr. Soc, 1888, p. 



544. 



Test free, conical, trochoid, consisting of an undivided, 

 compressed, spiral chamber; sutures limbate, externally with 

 a row of pits ; umbilicus depressed. 



Carboniferous. 



Genus TETRATAXIS Ehrenberg, 1843 

 Plate 23, figures 5-7 



Genoholotype, Tetrataxis conica Ehrenberg 



Tetrataxis Ehrenberg, Bericht. Preuss. Akad. Wiss. Berlin, 1843, p. 106. 

 Valvulina (part) H. B. Brady (not d'Orbigny), Pal. Soc. Mon. 30, 1876, 

 p. 81. 



Test conical, consisting of a proloculum and elongate second 

 chamber, later broken up into elongate, crescentic chambers 



