176 FORAMINIFERA 



Test free, of several chambers, irregularly arranged ; wall 

 arenaceous; aperture simple, terminal. 



Recent. 



This family includes those arenaceous forms which are typical- 

 ly trochoid at least in the early stages. In Nouria, the trochoid 

 character is not so marked, but in some species at least there 

 seems to be a loose spiral. 



FAMILY 20. PLACOPSILINIDAE 



Test attached ; chambers numerous and distinct, the early ones 

 often coiled or trochoid, interior simple or labyrinthic; wall 

 arenaceous; apertures of various forms. 



KEY TO THE GENERA 



I. Chambers simple, not labyrinthic. 



A. Early chambers close coiled, later uncoiled in a linear series, aper- 



ture simple Placopsilina. 



B. Test spreading, apertures numerous, peripheral Bdelloidina. 



II. Chambers labyrinthic. 



A. Aperture simple. 



1. Aperture, a crescent-shaped slit Haddonia. 



2. Aperture rounded, often with a neck Stacheia. 



B. Aperture cribrate, test cylindrical Polyphragma. 



C. Aperture, a ring of pores, test cylindrical Stylolina. 



Subfamily 1. Placopsilininae 

 Chambers simple, not labyrinthic 



Genus PLACOPSILINA d'Orbigny, 1850 



Plate 22, figures 11, 12 

 Genoholotype, Placopsilina cenomana d'Orbigny 



Placopsilina d'Orbigny, Prodr. Pal., vol. 2, 1850, p. 96. 

 Lituola Jones and Parker (not Lamarck), Quart. Journ. Geol. Soc, vol. 

 16, 1860, p. 302. 



Test attached, composed of numerous chambers, early portion 

 close coiled, later portions uncoiled and spreading out in a 

 generally linear series, last chambers sometimes free above the 

 attachment; wall coarsely arenaceous; aperture rounded, at the 

 end of the last-formed chamber. 



Silurian to Recent. 



