xlvi 



to him for the skulls and more or less of the skeletons of numerous species, 

 and among them of such forms as Polymixia, Scombrops, Etelis, Platyi- 

 nius, Brotula, Lucifuga, and the rarer forms of other families. I have 

 likewise, through the courtesy of the officers in charge, been able to make 

 free use of the Army Medical Museum. 



Acknowledgments are also due to Mr. J. CARSON BREVOORT, of Brooklyn, 

 and to Prof. 0. C. MARSH, and Mr. OSCAR HARGER, of Yale College, for 

 the loan of books, and other bibliographical facilities. 



In conclusion, the author begs to renew the assertion that the list is in 

 the strictest sense a temporary one, and merely preliminary to renewed 

 investigations, and that the sequence of families is not to be regarded 

 as the expression of the views of the author, except in part. The true 

 exposition of his present views respecting the system are embodied in the 

 preceding essay, and especially in the discussion of the sequence of forms. 



Comparative diagnoses, embodying the chief anatomical characteristics 

 of the orders and suborders in analytical tables, had been prepared for an 

 appendix to this volume, but it has been finally deemed by the author best 

 to defer the publication to a future time, and until he has been able to ex 

 amine the anatomy of several doubtful forms. Immediate insertion is the 

 less called for inasmuch as the remarks in the course of this introduction 

 will suffice to give an idea of the characters of most of the larger groups 

 adopted. 



