PLATE IX. 



a, b, c, </. ( , /'. first, second, third, fourth, tilth, and sixth side plates adjoining' the oral plate o. 

 </. food groove. 

 n, oral plate 



keel of oral plate 

 /», pores of perforated interradial plates adjoining food groove on the central part of the disk. 



1 Calcareous plates adj. lining the f 1 groove about one third the distance from the oral plates to the 



branch leading to the first pinnule. 



2 Perforated plates on the interradial part of the disk adjoining the line of imperforated plates. 



3. Magnified view of the calcareous network forming the pores,/), of the perforated interradial plates 



of the disk of Fig. 2. 



4. Reticulation surrounding one of the pores, p, of Fig. 2. 



5. Spongy reticulation surrounding the pores upon the proximal perforated plates. 



6. Optical section of the reticulation of one of the perforated plates, to show the irregular course of 



the canals formed by the pores, p. 



7. Slightly oblique profile of one of the oral plates and the adjoining side plates. 



8. The plates o, a, b, and c of Fig. 7 isolated, seen in profile. 



9. Another oral plate seen in profile from the right. 



10. The same oral plate seen facing the keel, o'. 



11. The other profile of the oral plate (see Fig. 9). 



12. Plate corresponding to plate a of Fig. 8 on the face of the adjoining food groove. 



13. The plate corresponding to b of Fig. S. 



14. The plate corresponding to c of Fig. 8. 



