EXPLANATION OF PLATE X. 

 (All figures after Clark.) 



PSAMMECHINUS CINGULATUS Clark, p. 288 



1-3. Dorsal, ventral and lateral views of a complete individual. 



4. Interambulacral area, enlarged. 



5. Three interambulacral plates highly magnified. 



6. Ambulacral area, enlarged. 



7. Four ambulacral plates, highly magnified. 



8. Oral opening, enlarged. 



9. Tubercle, enlarged. 



Vine en town limcsand. 



900 



