vi PREFACE. 



My share in the present volume has been small, having been confined to a careful perusal of 

 the sheets as they passed through the press, and a comparison of them with the original in 

 doubtful cases. I have likewise added a few foot-notes, indicated by my initials, and an 

 Appendix containing two papers from the Zoological Society's ' Proceedings ' which have imme- 

 diate reference to the present subject, a list of Nitzsch's published works, and a reprint of his 

 Memoir on the Carotid Artery of Birds. The latter is of special importance, as giving the 

 outline of the system of classification which he adopted, and which will, I believe, eventually 

 be found to be much more nearly correct than many schemes which have been subsequently 

 proposed. 



P. L. S. 



11, HANOVER SQUARE, LONDON; 

 Jan. 24th, 1867. 



