Xll 



Variations and Adaptations of the Rodents of the North Rim 



of the Grand Canyon, Arizona, by Floyd E. Durham 233 



Marine Algal Flora of the Caribbean and its Extension 



into Neighboring Seas, by Wm. Randolph Taylor _... 259 



A Preliminary Working Key to the Living Species of 



Dermatolithon, by E. Yale Dawson 271 



Structure and Evolution of the Sea Grass Communities 



Posidonia and Cymodocea in the Southeastern Mediterranean, 



by Anwar Abdel Aleem 279 



Nutrient Budgets in the Ocean, by K. O. Emery, 



Wilson L. Orr, and S. C. Rittenberg 299 



The Pleistocene History of the Channel Island Region, 



Southern California, by Thomas Clements 311 



Index of Scientific Names 325 



