CONTENTS 



page 



Introduction 3 



Acknowledgements 4 



Material and Methods 4 



Synonymy and Previous Descriptions 6 



Description of the Species 8 



S. fusiformis Cuvier .......... 8 



S. aspera Chamisso lo 



5. thompsoni sp.nov 1 1 



S. gerlachei sp.nov. 13 



Key to the Species 15 



Morphological Characters of Taxonomic Importance ... 15 



The number of fibres per muscle band ....... 15 



The arrangement of the body muscles 21 



The external character of the test 22 



The width of the body muscles in S. thompsoni and 5. gerlachei . . 23 



The development of the stolon in S. thompsoni and S. gerlachei . . 25 



Distribution 27 



Summary 29 



References 3° 



Appendix 3^ 



Plates I, II following p. 32 



