PREFACE. 13 



States National Museum I am indebted to Mr. Austin H. Clark and Miss Mary J. Rathbun. 

 Professor Verrill kindly gave me the opportunity to study the Recent Echini in Yale University 

 Museum. The authorities at Ward's Natural Science Establishment at Rochester liberally 

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

 in their charge, I am indebted also to Mr. Roy Miner, of the American Museum of Natural 

 History; Dr. F. A. Lucas, lately of the Brooklyn Institute of Arts and Sciences; Dr. A. S. 

 Pearse, of the University of Michigan; and Professor E. S. Morse, of the Peabody Museum at 

 Salem. Professor Morse also kindly gave me opportunity to study many Japanese Echini that 

 he collected in that country. Several gentlemen have most kindly supplied me with fine series 

 of specimens ; they are : Mr. A. P. Romine, of Bellingham, Washington ; Dr. W. K. Fisher, of 

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

 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, Massachusetts; Mr. 

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

 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 gave to the 

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

 and including 100 specimens, are now also in the collection of the same Museum. 



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 mj^ deep appreciation of the laborious painstaking care and skill with 

 which IVIr. J. Henry Blake made the larger part of the drawings for the plates and text-figures. 

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

 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 imperfections, 

 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 

 stud.y 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, except 

 as indicated by dotted lines. Of the text-figures, Mr. Blake drew figures 1 to 239 and 245 to 

 253, while figure 244 is the work of Mr. J. H. Emerton; figures 240 to 243 were done by Mr. 

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

 tions to Mr. F. A. Saunderson, of Boston, for the remarkable set of photographs of Echini 

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

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



