80 THE STRUCTURE OF AULACODISCUS MARGARlTACEUS. 



In the case of G. asteromphalus, I consider the markings in 

 each set of markings, as figured by Messrs. Nelson and Karop, 

 to be really those of a siliceous film across and slightly within 

 the mouth of each polygonal cell, as in Aulacodiscus margari- 

 taceus. If Coscinodiscus asteromjyhalus be examined from the 

 inner side of valve, " eye-spots " will be seen under a very 

 medium power. 



I think that further and careful examination undei suitable 

 lenses will show that all valves with " eye-spots " on the inner 

 surface of valve have their hexagonal, or rather polygonal, 

 cells, when present, closed on the outer surface, with delicate 

 siliceous films pierced with sets of extremely fine and minute 

 perforations. 



It must be understood that these remarks of mine in no way 

 apply to Triceratium favus, respecting which I must make 

 further examinations before offering a definite opinion relative 

 to its structure. 



