FAMILY 2. ASTRORHIZIDAE 65 



Genus CRITHIONINA Goes, 1894 



Plate 2, figures 14-16 

 Genotype, by designation, Crithionina mamilla Goes 



Crithionina Goes, Kongl. Svensk. Vet. Akad. Handl., vol. 25, no. 9, 1894, 

 p. 14. 



Test free, spherical, lenticular or variously shaped, interior 

 either with a large chamber and thin wall, usually perforated, or 

 with a small chamber and thick wall with the communication to 

 the surface by means of numerous branching tubes ; wall of 

 sponge spicules and very fine sand, often chalky in appearance, 

 soft, with little cement ; color white or grayish. 



Recent. 



The species are most abundant in cold waters where specimens 

 often occur in immense numbers. 



Genus VANHOEFFENELLA Rhumbler, 1905 

 Plate 2, fig-ures 17, 18 



Genoholotype, Vanhoeffenella gaussi Rhumbler 

 Vanhoeffenella Rhumbler, Verhandl. Deutsch. Zool. GeselL, 1905, p. 105. 



Test free, composed of a compressed chamber in the central 

 portion with a chitinous wall, the exterior a polygonal tubular 

 chamber with apertures at the angles, made of sand grains and 

 other agglutinated materials. 



Recent, at a depth of 400 meters. 



This genus may best be understood in its relationships by 

 imagining the central portion of a short-armed radiate 

 Astrorhiza to have the arenaceous material removed from about 

 the central portion leaving the thin chitinous wall and the result- 

 ing ring of arenaceous material cemented into a tube with the 

 arms reduced. 



The members of this family are very simple in structure; a 

 single chamber with numerous connections with the exterior, 

 either in one plane or spherical; wall of very slightly selected 

 material. Such forms are primitive and represent little more 

 than the chitinous members of the Allogromiidae with the mate- 

 rial of their environment built up about the channels by which 

 the protoplasm streams to the exterior. As they are usually 

 rather loosely cemented and difficult of recognition in the fossil 



