vi PREFACE. 



here, but as special attention has been paid to them in tlie Museum 

 at Cambridge, and as Professor Agassiz has introduced there a large 

 number of diagrams, all copied from original drawings, to illustrate 

 the structure and colors of animals which were too small or too 

 perishable to be preserved in the ordinary way, these valuable mate- 

 rials have been extensively used in the preparation of this Catalogue, 

 as forming actually a part of the collections exhibited in the show- 

 cases. The diagrams, as well as the authorities from which they are 

 taken, are carefidly enumerated below, after the specimens preserved 

 in the collection. 



For the facihties I have enjoyed in collecting the materials for this 

 Catalogue I am mainly indebted to Mr. and Mrs. J. M. Forbes, to Pro- 

 fessor A. D. Bache, Superintendent of the Coast Survey, to Mr. T. G. 

 Cary, and to Professor Agassiz. I have also to thank, for specimens and 

 valuable information. Professor Joseph Leidy, Dr. Fritz Miiller of De- 

 sterro, Dr. W. Stimpson, and Professor H. J. Clark, who had already 

 arranged the greater part of the Hj-droids before the collection of Aca- 

 lephs was placed in my charge. The Museum is also indebted for 

 specimens to many other persons, whose names will be referred to in 



connection with the different species. 



A. AGASSIZ. 



Cambridge, Mass., February, 1865. 



