FAMILY 2. ASTRORHIZIDAE 61 



Genus AMPHITREMA Archer, 1870 

 Plate 1, figure 13 



Genoholotype, Amphitrema ivrightiamim Archer 

 Amphitrema Archek, Quart. Journ. Micr. Sci., vol. 10, 1870, p. 122. 



Test short fusiform, the ends truncate and open, exterior with 

 foreign material. 



Recent. Fresh water, Ireland. 



For the most of the students who will use this book, the 

 Allogromiidae are of only slight interest. They are important 

 from the point of view of simple primitive types in the 

 foraminifera however, and figures are given of the important 

 genera. No fossil records exist as it is obvious that such tests 

 as they possess would not leave their records in fossilization. 



FAMILY 2. ASTRORHIZIDAE 



Test free, consisting of a central chamber from which radiate 

 tubular channels to the exterior, either simple or branching; 

 wall with a thin chitinous inner layer on all or part of which is 

 agglutinated arenaceous material ; apertures formed by the peri- 

 pheral ends of the arms or by openings in the peripheral wall. 



KEY TO THE GENERA 



I. Test with distinct arms or projections beyond the general periphery. 



A. Arms usually short, the central chamber large, \vall loosely 



cemented Af<frorhiza. 



B. Arms usually long, the central chambers small, wall firmly 



cemented Rhabdanimina. 



II. Test without distinct arms. 



A. Test generally spherical, thick walled, of fine arenaceous material. 



Crithio7m2a. 



B. Test generally flat and thin. 



1. Test entirely arenaceous, radiating arms distinct. Masonella. 



2. Test with only the periphery arenaceous, center thin and 



chitinous Vanhoeffenella. 



