Explanation op Plate 



CUona hackbernjensis, Thomas. 



The plate illustrates the characteristic borings of the species as seen on 

 valves of Stroplionella hybrida H. & W. 



In the two upper specimens figured the passages still contain more or 

 less of the original filling; in the lower right hand specimen the filling 

 has been nearly all removed leaving the passages open. 



The test of the lower left hand specimen, near the anterior margin, has 

 begun to crumble away due to being undermined by the numerous tunnels 

 beneath. 



The figures are nine-fifths natural size. 



168 



