NOTE, 



A small number of sea-urchins were collected during the Tropical Pacific 

 Expedition of the "Albatross" (1899-1900), so that only a few genera and 

 species characteristic of the Pacific will be described in succession whenever 

 sufficient new and interesting or important material has been obtained. 



The genus Colobocentrotus of Brandt remarkable for its peculiar primary 

 radioles forms the subject of the first part of the Tropical Pacific Echini. 

 This will be followed by a paper on the allied genus Heterocentrotus. 



I have to thank Mr. Richard Rathburn of the Smithsonian for having sent 

 me for study the types of Colobocentrotus collected at the Bonin Islands, by 

 Dr. Wm. Stimpson, the naturalist of the North Pacific Exploring Expedition 

 under command of Captains Ringgold and Rodgers. 



I am greatly indebted to Mr. Magnus Westergren for the interest he has 

 taken in the preparation of the Plates illustrating this Memoir. His accuracy 

 in drawing, his knowledge of the structure of sea-urchins obtained during his 

 long training in the preparation of plates on Echinoderms, is shown on every 

 plate due to his facile pencil. 



In addition to the material of Colobocentrotus collected by the " Alba- 

 tross " during the Tropical Pacific Expedition I have availed myself of mate- 

 rial collected by the " Albatross " at the Hawaiian Islands and in other parts 

 of the Pacific and in the Indian Ocean, found in the collections of the Museum 

 of Comparative Zoology. 



Alexander Agassiz. 



Newport, R. I., August 29, 1908. 



