226 PROCEEDINGS OF THE ACADEMY OF [1885. 



than existed in the United States at that time. Our materials 

 for study in the way of specimens have also been greatly aug- 

 mented, and for many of the advantages we possess in this 

 respect we are under extraordinary obligations to the naturalists 

 and collectors of the United States and Canada. Many of these 

 gentlemen, with rare liberality, have placed their collections at 

 our disposal, and forwarded to us, at the risk of loss in transit, 

 unique, valuable and original specimens. We desire to express 

 our grateful thanks for favors of this kind to Prof. Whiteaves, 

 Director of the Canada Survey ; Prof. Whitfield, of the American 

 Museum, New York ; Dr. C. A. White, of the Smithsonian Insti- 

 tution ; Prof. Worthen, Director of the Illinois State Survey ; Mr. 

 Walter R. Billings, of Ottawa ; Mr. S. A. Miller and Prof. Wetherby, 

 of Cincinnati ; Mr. I. H. Harris, of Waynesville, 0.; Mr. William 

 Gurley, of Danville, 111.; Mr. R. R. Rowley, of Curryville, Mo.; 

 Mr. James Love, of Burlington, Iowa, and others. We are also 

 under great obligations to our friend, Orestes St. John, who 

 executed the drawings which illustrate this paper. We consider 

 ourselves peculiarly fortunate in enlisting the co-operation, for this 

 purpose, of one who is both a trained and able naturalist and a 

 skilful artist. 



As a result of our recent researches, we have naturally been led 

 to entertain new ideas, and in some cases to a modification of 

 views at first entertained. 



In the present paper, which appears as Part III of the Revi- 

 sion, we give a description of the genera that have not been 

 considered in Parts I and II, and shall also state the results ot 

 our further studies in their bearing upon the genera heretofore 

 discussed. 



In the beginning of this work we recognized two great divisions 

 among Crinoids, viz. : Palaeocrinoidea and Stomatocrinoidea, for 

 the latter of which we afterwards adopted Carpenter's preferable 

 name Neocrinoidea. We divided the Paleeocrinoidea into three 

 great families, based upon as many distinct plans of structure. 

 We did not at first undertake to identify the different subgroups 

 into which these might be divided, except provisionally in some 

 instances, although we recognized the propriety of such subdi- 

 vision. Prof. Zittel had established twenty-two families of 

 Crinoids, and while his classification has great merit, and is in 

 many essential particulars in accordance with our own views, it 



