190 PROCEEDINGS OF THE AMERICAN ACADEMY 



XIV. 



PRELIMINARY REPORT ON THE ECHINI OF THE 

 EXPLORING EXPEDITION OF H. M. S. "CHAL- 

 LENGER," SIR C. WYVILLE THOMSON CHIEF OF 

 CIVILIAN STAFF. 



By Alexander Agassiz. 



[PUBLISHED BY PERMISSION OF THE LORDS OF THE ADMIRALTY.] 



Presented May 14, 1879. 



It was not my intention to publish a preliminary notice of the Echini 

 collected by the Challenger. I hoped to be able to issue the de- 

 scriptions of the species with my final report on the group. I am 

 compelled, however, for the sake of retaining for the material of the 

 Challenger expedition the priority of discovery, to notice briefly the 

 magnificent collection of Sea-urchins intrusted to my care by Sir 

 Wyville Thomson. The two expeditions of the U. S. Coast Sur- 

 vey steamer Blake, in which I was allowed, by the Superintendent 

 of the Coast Survey, to carry on very extensive dredging operations 

 in the Straits of Florida, the Gulf of Mexico, and the eastern part of 

 the Caribbean Sea, have brought together extensive deep-sea col- 

 lections, second only to those of the Challenger. In most of the 

 groups, judging from my recollection of the Challenger collections 

 when I had the privilege of examining them at Edinburgh, I should 

 say that the collections made on the Blake not only include dupli- 

 cates of the species of the Challenger, but numerous representatives 

 of the princijjal families collected by that expedition. I wish, of 

 course, as far as possible, to guard against any anticipation of the 

 results to be drawn from the older collections of the Challenger. 

 With the exception of certain Pourtalesite, of which I obtained only 

 a few perfect specimens on the Blake, (although numerous frag- 

 ments were constantly brought up by the trawl from depths of be- 

 tween 1,000 and 2,000 fathoms,) the Echini collected by the Blake 

 represent some of the most interesting forms obtained by the Chal- 

 lenger, and often complement more or less imperfect Challenger 



