NO. 6 ECHINOID DISTRIBUTION AND HABITS — KIER, GRANT 27 



mens were found in sandy patches that supported a growth of grass 

 within the reef. The species was found in depths ranging from 4 to 

 40 feet, and its abundance did not seem to be directly affected by 

 depth of water, but rather by the presence of turtle grass. 



The distribution of this species (fig. 6) slightly overlaps with that 

 of C. subdepressus. The two species occur together in the southern 

 part of the area investigated, where irregular patches of grass and 

 grassless sand are interspersed. 



This species was found at stations 2, 3, 4, 6, 7, 8, 9, 10, 11, 11a, 12, 

 13, 15, 19 (dead), 20, 21, 22, 23, 24, 26, 27, 29, 30, 33, 34, 44 (dead), 

 45, 47, 48, 50, 51, 52, and 53. 



Behavior — Clypeaster rosaceus does not burrow in the sand, but 

 travels on its surface. Normally it lives in fairly dense turtle grass, 

 where the tangled root systems just below the surface of the sand 

 prevent effective burrowing (pi. 3, fig. 3). Where individuals of this 

 species wander away from grass onto clean sand, they remain on the 

 surface and do not burrow. 



This species normally covers the upper surface of the test with 

 locally available coarse objects (pi. 4, figs. 1-7). The grassy habitat 

 provides a ready supply of blades of turtle grass, and the majority of 

 individuals used them for cover (pi. 4, figs. 1, 3, 6, 7). Most also 

 attached a few shells or shell fragments to themselves (pi. 4, figs. 3, 

 7) along with the grass or mangrove leaves and a little sand. Those 

 that were found away from the grass on sandy patches used shells, 

 shell fragments, sponges, and sand grains (pi. 4, figs. 2, 4, 5), but 

 some that were in relatively clean sand immediately adjacent to grassy 

 patches used a combination of grass and shell debris (pi. 4, figs. 1, 2, 

 4, 7) . C. rosaceus is rare on sand that is completely free of grass, but 

 when a specimen wanders far from its normal habitat it does cover 

 itself with sand exclusively, although it sorts it and uses the coarsest 

 grains (pi. 4, fig. 5). 



The purpose of the habit of holding grass, shells, or other objects 

 to the test has been a subject for controversy. Sharp and Gray (1962) 

 conducted a series of experiments on Lytechinus variegatus and 

 Arbacia punctulata to determine whether the habit of heaping shells 

 onto the test was related to sensitivity to light. They conclude that 

 L. variegatus is negatively phototactic, and that the habit of heaping 

 shells and other objects onto the test in the daylight is definitely related 

 to that character. They cite Boone (1928) to the contrary, who con- 

 tended that the purpose of the covering habit was to effect camouflage. 

 More studies such as that by Sharp and Gray, on more different kinds 



