ARENACEOUS FOEAMINIFEBA 



813 



stance of which very fine sand-grains are dispersed. This ' felt ' is 

 somewhat flexible, and its components do not seem to be united by 

 any kind of cement, as it is not affected by being boiled in strong 

 nitric acid ; its tendency, therefore, seems entirely due to the 

 wonderful manner in which the separate silicious fibres are * laid.' 

 It is not a little curious that these two forms should present them- 

 selves in the same dredging, and that there should be no perceptible 

 difference in the character of their sarcode bodies, which, as in the 

 preceding case, have a dark-green hue. The Marsipella elongata 

 (fig. 614, d), on the other hand, fcs somewhat fusiform in shape, and 

 has its two extremities elongated into tubes, with a circular orifice 

 at the end of each. The materials of the * tests ' differ remarkably 

 according to the nature of the bottom whereon they live. When 



FIG. 614. Arenaceous Foraminifera : , b, upper and lower aspects of Haplo- 

 phragmium globigeriniforme ; c, Hormosina globulifera ; d, Marsipella 

 elongata ; e, terminal portion, and /, middle portion of the same, enlarged ; 

 g, Thurammina papillata ; h, portion of its inner surface, enlarged. 



they come up with ' Globigerina mud,' in which sponge-spicules 

 abound, whilst sand-grains are scarce, they are almost entirely 

 made up of the former, which are ' laid ' in a sort of lattice-work, 

 the interspaces of which are filled up by fine sand-grains ; but when 

 they are brought up from a bottom on which sand predominates, 

 the larger part of the ' test ' is made up of sand -grains and minute 

 Foraminifera, with here, and there a sponge-spicule (fig. 614, d,f). 

 In each case, however, the tubular extensions (one of which some- 

 times forms a sort of proboscis, e, nearly equalling the body itself 

 in length) are entirely made up of sponge-spicules laid side by side 

 with extraordinary regularity. The genus Rhabdammina (Sars) 

 resembles Saccammina in the structure of its ' test,' which is com- 

 posed of sand-grains very firmly cemented together ; but the grains 



