66 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 149 



by passing sand up through notches and lunules (time: 2:31). Both species 

 started at watch band. 



7. Both specimens have achieved nearly the same proportion of cover, 

 but E. michelini has moved farther forward (time 2 :34). 



8. Both nearly buried ; E. michelini moved forward about one length, 

 (time: 2:35). 



Plate 8. PLAGIOBRISSUS GRANDIS BURYING 



1-4. Timed series illustrating manner and speed by which excavated specimen 

 of Plagiobrissus grandis (Gmelin) buries itself, station 30 (depth 15 feet). 



1. Time 3:09. Sand beginning to form ridge around specimen; process 

 began about 1 minute earlier. 



2. Time 3:10. Specimen buried to nearly half its own thickness, pushing 

 up large rim of displaced sand. 



3. Time 3:12. Upper surface of specimen at level of surface of sand; 

 sand from rim being drawn onto test. 



4. Time 3:15. Test nearly covered, long dorsal spines projecting through 

 sand. 



5. Partly buried specimen at station 30 (depth 15 feet), showing long dorsal 



spines. 



6. Side view of partly buried specimen at station 23 (depth 12 feet) showing 



backward curvature of long dorsal spines ; rim of displaced sand destroying 

 small ripple. 



Plate 9. GROWTH SERIES IN MEOMA VENTRICOSA 



1-4. Specimens showing change in test shape, length and arrangement of petals, 

 size of peristome, and size of tubercles during growth. 



1. Specimen 22 mm. long (X2); station 19; USNM E10315. 



2. Specimen 44 mm. long (X 1) ; station 17; USNM E10314. 



3. Specimen 71 mm. long (X0.6); station 30; USNM E10313. 



4. Specimen 144 mm. long (X0.3; station 17b; USNM E10312. 



Plate 10. MEOMA VENTRICOSA 



1-4. Meoma zentricosa (Lamarck) 



1. 2, 3. Adapical, adoral, right side of immature specimen, 22 mm. long, 

 Rowing spines (X2.5); station 19; USNM E10315. 



4. Adoral view of adult showing difference in length of spines from 

 immature specimen (X2.6); station 17b; USNM E10312. 



5. Arbacia puiictulata (Lamarck). Station 27; USNM E10320. Adapical view 



of naked test (X VA). 



6. Echinovictra z-iridis Agassiz. Station 3; USNM E10319. Adapical view of 



dried specimen (XI). 



Plate 11. MEOMA VENTRICOSA IN SAND 



1-6. Meoma ventricosa (Lamarck) burrowing in sandy bottoms. 



1. Partly buried specimen with depressed petal area being nipped by 

 small parrot fish (Sparisoma aurojrenatum). Others nearby with dorsal 



