INTRODUCTION. 



THIS memoir contains a description of the rich collection of Deep-Sea Alcyon- 

 arians made by the Royal Indian Marine Survey Ship " Investigator " in the 

 Indian Ocean. 1 It will be followed by another dealing with the littoral forms. 



The collection includes eighty-six species, of which sixty-one (and three 

 varieties) are new. It has been found necessary to establish five new genera, 

 Stereacanthia and Agaricoides in the family Nephthyidse, subfamily Siphono- 

 gorginse ; Acanthomuricea and Calicogorgia in the family Muriceidse ; and 

 Thesioides in the family Kophobelemnonidae. The general position of the new 

 forms is as follows : 



Order I. Stolonifera 

 II. Alcyonacea 

 III. Pseudaxonia . 



IV. Axifera . 



V. Stelechotokea . 



1 I wish to thank Professor A. Alcock, LL.D., F.R.S., Superintendent of the Indian Museum, for giving 

 me the opportunity of studying this fine collection of beautiful forms, and the Trustees of the Indian Museum 

 for a grant towards expenses. Through the Carnegie Trust I was able to secure the help of Mr. W. D. 

 Henderson, joint author of this memoir, whose work in this connection was in part done during his tenure 

 of a Carnegie Scholarship and Fellowship. We are greatly indebted to Mr. ( !eori;e Davidson, artist, for the 

 skill and patience which he has bestowed on the illustrations. We think that the engraver, Mr. Edwin 

 Wilson, also deserves to be congratulated on his success, for the coloured plate.- iu particular piv 

 unusual difficulties which have been happily overcome. Finally, I wish to acknowledge my great indebted- 

 ness to my private assistant, Mr. .lames J. Simpson, M.A., B.Sc., without whose aid the completion of the 

 memoir would have been much delayed. His skill will be seen in the description of the remarkable genus 

 Agaricoidet. Dr. J. Versluys, of Amsterdam, most generously gave me his notes on ' .ami 



Professor S. J. Hickson, F.R.S., of Victoria University, Manchester, was kind enough to allow me to consult 

 his fine collection, and to lend me some of the literature. J. A. T. 



