NOTES ON AN OSTRACOD AND OSTRACODAL LIMESTONE. 247 



To give some idea of the great abundance of these little 

 organisms that have drifted into the empty chamber of an 

 Orthoceras shell, I counted over an average portion of the 

 slide, which gave the result of 20,000 individuals in 1 cubic 

 centimetre. 



Occurrence. — In an infilling of an Orthoceras shell from 

 the Parish of Taemas, New South Wales. 



Explanation op Plate. 

 Fig. 1. Primitia yassensis, sp. no v. The specimen, a left valve, 

 seen from the side. Middle Devonian, Taemas, near 

 Yass. x 26. 



Fig. 2. P. yassensis, sp. nov. Outline of valve, edge view, x 26. 



Fig. 3. P. yassensis, sp. nov. Ornament of valve, somewhat 

 restored, seen near the ventral margin. x 52. 



Fig. 4. Photomicrograph of an ostracodal limestone with Primitica 

 etc., from Taemas, near Yass 



