spongin of sponges, and is the colloid medium through which, I 

 believe, the siliceous solutions diffused in the formation of beekite. 

 The fact that aragonite is more easily dissolved and replaced than 

 calcite depends almost entirely on the nature of the organic matter 

 of the shell. 



An interesting discussion followed, in which Mr. Robert Bell, 

 Mr. S. Wear, Mr. R. May, and the Chairman of the meeting 

 took part, and Mr. Strachan's fine collections were then carefully 

 examined. 



DESCRIPTION OF PLATE XX. 



Fig. i. — Exterior of Exogvra columba from Chloritic 



Sands, Colin Glen, near Belfast ; coated heavily 



with beekite, x *y 2 diameters. Photographed 

 from fossil embedded in situ. 



Fig. 2. — Typical microscopic appearance of beekite 



by reflected light, x 10 diameters. From Exogyra 

 columba as above. 



-©X'K^ 



