PLATE lY. 



ac, canal leading to arm. 

 g, food groove. 

 pn, pinnule. 

 pn', first pinnule. 



St, subtentacular canal. 

 »•, first radial. 

 *. sjzygy. 



1. Arm of left anterior radial of a broken specimen, |. 



2. Slightly oblique view of vault, showing the relation of the interradial plates of the vault and the 



plates covering the subtentacular canal and the food groove, ^. 



3. Interior view of upper part of perisomatic vault, showing food groove, the subtentacular caual, and 



the extension of the cceliao cavity as a groove into cavity of the arm, «. 



4. The same as above, seen edgewise. 



5. Interior view of upper pai-t of interradial space, showing its connection -with the edge of the arm 



joints and of the pinnules, ^■ 

 G. Interior view of lower interradial plates, j. 



7. Base of the first pinnule, showing the connection of the lower interradial plates to the pinnule joints 



and to the smaller perisomatic plates, seen in profile. * 



8. Showing spongy character of the upper perforated perisomatic plates, magnified. 



9. Exterior upper face of an imperforate interradial plate in the second row. 



10. Lower interior face of the same. 



11. One of the plates of the first row of interradials, exterior face. 



12. Another plate from the first row of interradials, exterior face. 



13. Plate of Fig. 11 seen edgewise to show its thickness. 



14. One of the smallei' imperforate interradial plates near the edge of fourth radial. 



15. 16. Magnified views of reticulation of the interradial plates. 



