22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 149 



Moore et al. ( 1963, p. 24) state that L. variegatus is intolerant of 

 suspended silt in the water. However, we found the species to be 

 abundant in the Hawk Channel where the water is continuously cloudy 

 with suspended silt, at least during the summer (C. Pontin, personal 

 communication). 



The pattern of distribution of L. variegatus is remarkably similar 

 to that of Clypeaster rosacens, another grass-dwelling species (figs. 5, 

 6) . On the other hand, it shows little overlap with the distribution of 

 C. subdepressus or Meoma ventricosa, two species that prefer the 

 clean sand habitat, and apparently prefer to live somewhat farther off 

 shore. 



According to Moore, et al. (1963) the minimum depth range of this 

 species may be determined by two factors. One is that specimens 

 exposed at low tide are seized by gulls which carry them to a height 

 and drop them to crack them and expose their edible insides. The 

 other is that the species is remarkably sensitive to short ultraviolet 

 rays, which are filtered out by a few inches of water, as shown by 

 Sharp and Gray (1962). Therefore, the net effect is to keep the 

 population of L. variegatus confined to depths greater than those 

 exposed at low spring tides. 



The maximum depth at which this species lives probably is deter- 

 mined by the depth range of turtle grass (Thalassia) , which is about 

 35 feet (Moore, et al., 1963). We found the species only in waters 

 shallower than that depth, and essentially inshore from the "interreef 

 deep channel." 



This species was found at stations 2, 3, 4, 6, 7, 8, 9, 10, 11, 22, 24, 

 27, 28, 29, 30, 31, 33, 35, 46, 48, 51, 52 and 59. 



Behavior. — Lytcchinus variegatus lives above the surface of the 

 sand, moving over the sand and the turtle grass, and climbing up 

 among the blades of grass. Dissections of several specimens, and 

 observation of activities of others, confirm that this species feeds 

 mainly on turtle grass (Moore, et al., 1963). 



This species, like some other nonburrowers, covers its test with 

 objects from the bottom, holding them by its tube feet (pi. 3, fig. 1). 

 Broad objects that cover much surface seem to be preferred. Indi- 

 viduals that live near shore nearly uniformly hold one or more man- 

 grove leaves onto the test, and farther from shore where mangrove 

 leaves are scarce, some individuals managed to find one. Others use 

 complete clam valves, or other large fragments of shell, and many use 

 the blades of turtle grass for cover. Experiments by Sharp and Gray 

 (1962) suggest that this species covers itself to avoid sunlight, al- 



