PLATE IV. 

 Orthis Vanuxemi. 



Page 75. 



Fig. 1. Vertical longitudinal section through a portion of the test, showing 

 the laminae of the shell and tubuli. Some of the tubuli bifur- 

 cate before reaching the surface. 



Fig. 2. Vertical longitudinal section through the front of two valves, showino- 

 very distinctly the oblique laminae and the size of the vertical 

 tubuli. 



Fig. 3. Horizontal section from near the surface, showing large and small 

 punctae. 



Fig. 4. Section from near the center of a valve, showing the fibrous and 

 punctate structure. 



Fig. 5. Section at some depth below the surface, showing the regular rows of 

 punctae and flexuous direction of the fibres which run inde- 

 pendently of the rows of punctae. 



Orthis Penelope. 

 Page 75. 

 Fig. 6. Horizontal section showing the very strongly marked rows of punctae 

 and intermediate fibrous structure. 



SCHIZOPHORIA MULTTSTRIATA. 

 Page 75 . 



Fig. 7. Showing the numerous minute punctae and fibrous structure of the 

 shell of this species. 



SCHIZOPHORIA IOWENSIS. 



Page 75. 

 Fig. 8. A section from near the surface, showing the numerous punctae. In 

 sections cut at a greater depth the appearance is similar in 

 general features to fig. 9. 



SCHIZOPHORIA TULLTENSIS. 

 Page 75. 

 Fig. 9. Showing the numerous close punctae with no definite arrangement. 



SCHIZOPHORIA IMPRESSA. 

 Page 75. 

 Fig. 10. Section from nearer the surface than the preceding, showing the 

 broad bands of punctae which gradually coalesce and produce 

 an evenly punctate structure. 



