INTRODUCTION. XJ 



of Natural Sciences of Philadelphia allowed me, through Professor Leidy, 

 access to their collection containing many interesting species, especially 

 from the South Pacific. Professor Verrill has invariably communicated 

 to me with the greatest readiness the species he was describing from the 

 Museum of Yale College. To Mr. Putnam I owe many valuable speci- 

 mens from the collections of the Essex Institute, principally from Zanzi- 

 bar and other portions of Africa. 



The collection of the Museum of Comparative Zoology itself contains 

 the types of the majority of the species of the Catalogue Raisonne ; 

 the immense collections of Eehinoderms made by Mr. A. Garrett at va- 

 rious points in the Pacific Ocean, by Mr. C. Cook at Zanzibar, by Mr. 

 Henry Edwards in New Zealand and Australia, by Mr. Thomas G. Cary at 

 San Francisco ; the collections of the eastern coast of the United States 

 from Maine to Florida, made by Professor Agassiz ; the collections of 

 the Thayer Expedition in the West Indies and Brazil ; a collection of 

 Mediterranean species made by Professor Panceri ; the collections of Mr. 

 Pourtales from the deep waters between Florida and Cuba ; my own 

 collections from Panama, the west coast of Mexico, California, and the 

 Gulf of Georgia, besides innumerable exchanges made with other mu- 

 seums which will be noticed in their proper places. 



The material accumulated in Cambridge represents, with but four 

 or five exceptions, every species described during the last forty years. 

 A good deal of unpublished matter collected by Professor Agassiz for 

 the continuation of his Monographies d'Echinodermes has been incorpo- 

 rated in this Revision. The freest use has also been made of prepara- 

 tions made under his direction by the late Nathaniel Bowditch, and of 

 a collection of sections of spines of Echini begun by Mr. Glen and con- 

 tinued by Mr. Bicknell with admirable success. Mr. Bicknell has also 

 made for the Museum microscopic preparations of such pedicellaria3 and 

 spicules as have been found necessary. 



For the careful execution of the lithographic plates I am indebted to Mr. 

 P. Roetter ; to Mr. A. Sonrel for the preparation of the negatives needed for 

 the "Woodbarytype and Albertype processes which have been employed for 

 some of the Plates of this Revision. I have also to thank Messrs. E. Bier- 

 stadt, of New York, and John Carbutt, of Philadelphia, for the trouble they 

 have taken in making the necessary adaptations of their methods of printing 

 to the needs of Natural History illustrations. 



