192 CRIBRILINID.E. 



that which I have characterized as var. ; but it appears 

 in a multitude of guises, and in some of them is very 

 unlike its proper self. The cells are usually somewhat 

 elongate, but occasionally short and almost orbicular. 

 The normal arrangement of the punctures is in transverse 

 rows ; but the rows are often very inconspicuous, and in 

 many cases the pores are scattered thickly over the sur- 

 face. Down each side of the cell several erect nodulous 

 processes are not unfrequently ranged, whilst one of 

 larger size is placed centrally at the base. In one very 

 marked variety the punctures are arranged in rows ex- 

 tending from near the margin to an elevated median keel 

 or crest, and occupy an oval space on the front of the cell, 

 which is inclosed by a line of minute raised pores. The 

 lower margin of the orifice is always thickened and more 

 or less mucronate ; but in some cases it becomes very 

 massive and bears a broad, projecting expansion in front. 

 At times on the inner margin there is a bifid process. 

 Probably the ooecium is more variable in appearance than 

 any other portion of the structure; it is sometimes 

 smooth and silvery, with a raised thickened rib across it 

 in front, rising in the centre into a knob. In some cases 

 it is covered with raised punctures and numerous nodules, 

 and bears a small elevated avicularium at the top ; in 

 others, again, it is smooth, and so much immersed as to be 

 hardly visible, the thick and often subtriangular rib alone 

 standing out prominently above the orifice. Occasionally 

 it is elongated and punctured. 



The species, it will be seen, is liable to great diversities 

 in what may be called its surface-decoration. In fresh 

 specimens the cells are silvery and bright ; but there is 

 more than the usual tendency to thickening and opacity 

 in the older states. 



