CRIBRILINA PUNCTATA. 191 



confluent, disposed in lines, the whole front perforated 

 with punctures of varying size and shape, in rows, or 

 sometimes irregularly distributed : orifice transversely 

 oblong, lower margin ranch thickened, projecting into 

 a prominent mucro ; marginal spines four or five, the 

 two foremost curved in fertile cells, meeting across the 

 mouth in front of the ooecium j an avicularium on each 

 side of the orifice (sometimes on one side only), with 

 pointed mandible, directed obliquely upwards. Ocecia 

 rounded, smooth, and vitreous, sometimes with a strong 

 rib in front, inclosing a triangular space, from which a 

 keel passes oflF to the base ; frequently a raised process 

 immediately behind it supporting a small avicularium ; 

 sometimes destitute of the rib and keel, and thickly 

 punctured. 



Pohjpide tall and very delicate, with about 13 tentacles. 



Primary cell small, with a large, terminal, orbicular 

 orifice, surrounded by twelve spines. 



Colonies forming silvery shining patches when young, 

 much thickened and coarser when old, with a tendency 

 to a subcircular growth. A central group of diminutive 

 cells marks the origin of the colony. 



Var. a. With a central umbo, from which ribs pass off to 

 each side, rising into erect processes round the front of 

 the cell, usually a single large pore in each furrow ; 

 mucro and marginal spines strongly developed ; lateral 

 avicularia in a line with the lower margin of the orifice, 

 the mandible directed straight outwards. Ooecium covered 

 with spinous projections, and commonly with a raised 

 avicularium on the hinder part of it. 



Range of Variation. This is a species of very variable 

 aspect. The changes in its appearance are chiefly due to 

 the greater or less development of various nodulous and 

 other processes on the surface of the cell and ovicell. 

 Perhaps the most remarkable form which it assumes is 



