NO. 6 ECHINOID DISTRIBUTION AND HABITS KIER, GRANT 



45 



widely separating the posterior oculars. Some madreporitic pores also 

 occur in genital plate 1. Mortensen (1951, p. 529) reports that genital 

 pores appear in Meoma grandis Gray when the echinoid is about 50 

 mm. long. 



B 



Fig. 13. — Change in subanal fasciole 

 during growth of Meoma ventri- 

 cosa (Lamarck). In the smallest 

 specimen, 22 mm. long, that portion 

 of the fasciole near the periproct 

 is broad but decreases in width dur- 

 ing the growth of the echinoid and 

 is absent in an adult. A. USNM 

 E10315; station 19; 22 mm. long; 

 X 3; B. USNM E10314; station 17; 

 44 mm. long; X 1.7; C. USNM 

 E10313; station 30; 71 mm. long; 

 XL 



In one of the larger specimens, 144 mm. long, the last plates (adapi- 

 cal) in the posterior interambulacrum are not in contact with the 

 posterior oculars. As shown by Kier (1956, p. 971) this separation 

 indicates that production of new interambulacural plates has ceased 

 in this area. 



