38 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 149 



probably preyed upon P. grandis by burrowing, a surmise supported 

 by Moore's extensive observations on this activity. 



Genus BRISSUS Gray 

 BRISSUS UNICOLOR (Leske) 



Plate 15; figures 4, 5 



This small spatangoid, usually around 50 mm. long, has an elon- 

 gated test inflated posteriorly, a blunt anterior margin, and a rather 

 pointed posterior margin. The living test is white to light tan, has 

 short spines, and very obvious black pedicellariae. Only four petals 

 are present, the anterior pair are short and diverge 180 degrees. This 

 species differs from the only other small spatangoid found with it, 

 Schisaster {Par aster) floridiensis, by its more elongate test, shorter 

 spines, longer posterior and shorter anterior petals, and less depressed 

 anterior ambulacrum. 



Occurrence. — This relatively rare species was found living under 

 rock slabs in and near the reef. Dead tests were found in sandy areas 

 near the reef, except for one found near an almost completely disin- 

 tegrated shipwreck supporting an incipient growth of coral, sponge, 

 and algae that probably was the ecological equivalent of a small reef 

 patch. Living specimens on the reef occurred in about 15 feet of 

 water, but dead tests were encountered in depths from 18-80 feet. 



Mortensen (1951, p. 512) suggested that the species lives buried, 

 which accounts for its apparent rarity. We found it living under 

 rocks, but could not determine confidently whether it was clinging to 

 the undersur faces of the rocks, or was in the sand beneath them. The 

 ease with which they drifted out of the hole that was left when a slab 

 was overturned suggests that they were not clinging to the rock, but 

 were living in the coarse sand under it. 



Dead tests were found at stations 17a, 19, 21, 30, and 44; living 

 specimens at station 60. 



Genus MEOMA Gray 



MEOMA VENTRICOSA (Lamarck) 



Plate 3, figures 4, 5; plate 9, figures 1-4; plate 10, figures 1-4; plate 11 figures 



1-6; plate 12, figures 1-4; plate 13, figures 1-3; plate 15, figure 6; plate 16, 



figures 5, 6 ; text figures 8-14 



This large spatangoid (150 mm. long) has a high brown test cov- 

 ered with relatively short spines. The bare dead test is white and has 



