NOTE. 



With the permission of Professor Peirce, the Superintendent of the Coast 

 Survey, I have been able to incorporate in my Revision of the Echini the 

 Report on the Deep Sea Echini collected by Count Pourtales in 1867-1869, 

 while in charge of the expeditions made for the exploration of the Gulf 

 Stream by the United States Coast Survey, in the steamers Corwin and 

 Bibb, Acting Master Robert Piatt, U. S. N., commanding. As this Report 

 includes nearly all the species found on the eastern coast of the United 

 States, two of the northern species not actually found by Count Pourtales 

 have been added to the Report, to make it as far as possible a complete 

 picture of the Echini of the Atlantic coast of the United States. This Was 

 the more advisable, as, both these species having been very fully examined 

 in all their earlier stages of growth, they were of essential assistance in the 

 study of the small Echini collected by Mr. Pourtales. 



From the large number of small-sized Echini collected by Mr. Pourtales 

 it became necessary, in order to study them intelligently, to examine the 

 young of as many species as possible, and obtain some criterion by which to 

 determine this collection accurately. The results to which this examination 

 led me formed the basis of the Preliminary Report, published in the Museum 

 Bulletin, in which was given, as far as it could be done without figures, a 

 short resume of the conclusions to which I have been led by the study of 

 these young, leaving for this Report a detailed description, as well as 

 figures, of the changes there mentioned, which these young undergo. Some 

 of the specimens collected by Mr. Pourtales are so small that they must 

 have absorbed their Pluteus very recently before their capture. This col- 



