460 SYSTEMATIC TALEOXTOLOGY 



Order FORAMINIFERA. 



Suborder VITRO-CALCAREA. 

 Family NUMMULINID/E. 

 Genus NONIONINA d'Orbigny. 

 The genus Nonionina is so closely related to Polystomella that some 

 authors consider that it should l^e allowed to lapse or at best be considered 

 as onl}^ a subgeneric group of the true Polystomella type. Typically 

 the shell is convolute with equilateral compression as in Anonuiliim so 

 that it presents a symmetrical nautiloid form in which the final volution 

 embraces all the others. The umbilicus is either depressed, flush, or filled 

 with exogenous substance as in N. asterizans, and the septal markings are 

 more or less depressed though the amount of depression varies with every 

 species. The shell substance is hyaline, and distinctly perforate, often 

 finely so. The aperture is situated on the inner margin of the ultimate 

 segment and is either an arched fissure or subdivided into a number of 

 jwrous openings as by some PohjstomelUe. The genus does not seem to l^e 

 recorded prior to the beginning of the Tertiary. At the present time 

 it occurs at all depths and is cosmopolitan in distribution occurring in 

 every latitude. 



XoxioxiXA SCAPHA ( Fichtel and 3Ioll). 

 Plate CXXXI, Figs. 1, 2, 3. 



Nautilus acapha Fichtel aud Moll, 1803, Test. Microsc, p. 105, pi. xix, tigs. d-f. 

 Nonionina scapha Brady, 1884, Cbal. Kept., vol. ix, p. 7o0, pi. cix, ligs. 14, 15 (and 



16 ?). 

 Nonionina xcapha Bagg, 1898, Bull. Amer. Pal., No. 10, p. 41, pi. iii, figs. 4a, 4b. 



Description. — Test free hyaline, finely perforated, elongaJ;e, rather 

 strongly compressed, peripheral margin broadly rounded, chambers num- 

 erous, narrow, long, rapidly increasing in size toward the ultimate cham- 

 ber and separated by nearly straight septal lines; sutural limbations 

 becoming more marked towards the ultimate chaml)er which is the 

 largest and longest and extends fully two-thirds the length of the entire 

 shell. Septal plane l)roadly oval or cordate; convolutions about three, 

 twelve to fourteen chambers in the final volution; aperture a small con- 

 centric slit situated on the inner margin of the ultimate chamber. 



