I'I!KF\( !:. , ;{ 



States National Museum I am indebted to Mr. Austin H. Clark and Mi m Mary J. Hathhun. 

 Professor Verrill kindly gave me the opportunity to study the Recent KHuni , Yale Unfa 

 Museum. The authorities at Ward's Natural Science Establishment at |{,,,.|,,M,.r literally 

 allowed me to study their large trade collection. For opportunities to stiifh material 



in their charge, I am indebted also to Mr. Roy Miner, of the Ameriean Ma-mi, d 

 History; Dr. F. A. Lucas, lately of the Brooklyn Institute of Arts and Science*; Dr. A .- 

 Pearse, of the University of Michigan; and Professor E. S. Morse, of (in- IVabody Museum at 

 Salem. Professor Morse also kindly gave me opportunity to study many .la], him that 



he collected in that country. Several gentlemen have most kindly supplied me with (in,- - 

 of specimens; they are: Mr. A. P. Romine, of Bellingham, Washington; Dr. \V. K. 1 i-l, 

 Stanford University; Professor W. E. Ritter, of the University of California; Professor 1 

 Mark, of Harvard University; Dr. H. C. Chadwick, of the Port Erin Biological Station: Dr. 

 F. D. Lambert, of Tufts College; Dr. Thomas Barbour, of Cambridge, Massachu-ett-; Mr. 

 Dwight Blaney and Mr. Owen Bryant, of Boston. Dr. Theodor Mortensen kindly loaned . 

 valuable material and helped me by correspondence. 



In addition to material studied in various institutions, my work has been based on my 

 own collection of some 40,000 Recent and Mesozoic Echini. These I recently nave to the 

 Museum of Comparative Zoology. My Palaeozoic Echini, accumulated during many \ 

 and including 100 specimens, are now also in the collection of the same .Mu.-eum. 



I would express my warm obligations to my friend, Mr. Samuel Henshaw, Curator of the 

 Museum of Comparative Zoology, for the use of a room and for the use of the great library- 

 facilities there afforded. 



I would express my deep appreciation of the laborious painstaking care and skill with 

 which Mr. J. Henry Blake made the larger part of the drawings for the plates and text-fij:' 

 It is very difficult to get an artist who can draw a sea-urchin correctly, and without Mr. Blake'- 

 skill and patience I should have been badly handicapped. Any sea-urchin is difficult to draw 

 accurately, but in the Palaeozoic, one has to contend with the difficulties of imperfect 

 often the fusion or indistinctness of sutures; the fossils are frequently external or internal 

 molds or siliceous replacements, and these conditions add much to the difficulties of critical 

 study and correct interpretation. The drawings were all made under my eye, and are as faith- 

 ful to the originals as it was possible to make them. No restorations were permitted. e\ 

 as indicated by dotted lines. Of the text-figures, Mr. Blake drew figures 1 to 230 and '_'! 

 253, while figure 244 is the work of Mr. J. H. Emerton; figures 2-10 to 2-13 were done by Mr. 

 A. H. Searle, and figures 254 to 256 by Mr. William M. Barrows. I would also expn obliga- 

 tions to Mr. F. A. Saunderson, of Boston, for the remarkable set of photograph- >f Kchini 

 which are reproduced as heliotypes. Some of the drawings and photographs were made by 

 other artists in Europe or this country, as mentioned in the description of plates. The illu 



