2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I49 



and therefore can live in grassy areas. Less commonly it leaves the 

 grass and moves over the surface of clean sand. Meoma ventricosa 

 (Lamarck) normally burrows in areas of thick grassless sand rela- 

 tively far from shore. It was observed rarely on the surface of the 

 substrate, in grass or on clean sand, with debris held onto the test in 

 the manner of C. rosaceus. Plagiobrissus grandis (Gmelin) burrows 

 in clean sand, and was never observed at the surface. Brissus unicolor 

 (Leske) and Echinaneus cyclostomus Leske live in coarse sand be- 

 neath rocks in the vicinity of the reef. 



The only species not observed alive is Schizaster (Paraster) fiori- 

 diensis n. sp., which also has been found off the coast of the island of 

 Dominica in the southern Caribbean. 



INTRODUCTION 



Echinoids are important constituents of the near-shore marine 

 biota, contributing significantly to the food-chain and to modification 

 of the substrate. In some areas they are among the most abundant 

 megascopic animals. Similarly, their remains are abundant as fossils, 

 especially in younger geologic strata, and as such they have become 

 important indicators of the ages and environments of deposition of 

 many Tertiary formations. These animals have been studied by zoolo- 

 gists and paleontologists since the beginnings of those sciences, and 

 much has been learned about their evolution, gross areal distribution, 

 general biology, habitat preferences, and especially their taxonomy. 

 Nevertheless, until the invention of self-contained underwater 

 breathing apparatus it remained virtually impossible to observe in 

 detail the living habits and local habitat preferences of any but inter- 

 tidal species. The authors are paleontologists whose prime concern is 

 to interpret the ecology and life-habits of fossil animals, normally 

 through recourse to the literature of biology and ecology. However, 

 detailed data on the habits and habitats of living echinoids is scarce, 

 therefore it was necessary to make firsthand observations. 



The results of this preliminary study are presented in order to 

 provide a broad ecological framework for further such studies in 

 other areas, and for more detailed and comprehensive investigations 

 of individual species. 



Location and methods. — The Key Largo Coral Reef Preserve is 

 an area almost completely under water which has been set aside by 

 the governments of the United States and Florida for the preservation 

 of a living coral reef and its surroundings (fig. 1). The administration 

 is under the State of Florida, which has named its on-shore facilities 



