Plate 8. 



1-9. Porocidaris Milleri A. Ag. 



Figs. 1-3 show the formation of the new ainbulacral plates below the ocular plates, seen 

 from the interior of the test of a specimen 33 mm. in diameter ; Station 3415. 



1. The odd ocular plate and young ambulacral plates. 



2. The ocular plate of the right anterior ambulacrum. 



3. The ocular plate of the left posterior ambulacrum. 



4. The odd anterior ocular and the young ambulacral plates, seen from the exterior the 



same as fig. 1. 



5. The actinal ])hites of the odd anterior ambulacrum with the adjoining buccal plates and 



surrounding interambulacral plates of a specimen 33 mm. in diameter. 



G. Abactinal system of the same specimen as fig. 5, seen from the interior of the test, 

 the anal system pushed to one side, and the left posterior genital split in two. 



7. The fifth primary tubercle from the actinal system in the right posterior iuterara- 



bulacrum, specimen 28 mm. ; Station 3381. 



8. The auricles of the right anterior ambulacrum, seen from the interior of the test, same 



specimen as fig. 7. 



9. The same as fig. 8, seen from the exterior. 



