vi PREFACE 



In the section of the book dealing with Vertebrata many 

 changes have been made. In the chapter on Fishes, we 

 have endeavoured to bring clearly before the student's mind 

 that the existing piscine population of the world's waters consists 

 of two types of fish, the bony and the cartilaginous, and that the 

 so-called Ganoids and Dipnoi comprise very few species, the 

 last survivors of groups now nearly extinct. Sketches of the 

 modern classification of Bony Fish and of Birds have been 

 given so that the student may grasp to some extent the principles 

 on which modern systematists proceed. Lastly, in the section 

 dealing with Mammalia, considerable alterations were inevitable. 

 Our largely increased knowledge of Theromorphous Reptiles 

 has rendered untenable the view of the hornology of the ear- 

 ossicles of Mammalia formerly accepted by us, and the brilliant 

 discoveries of Dr Andrews have settled the position of Elephants 

 and Sirenia. 



Besides those whose work we have mentioned above we owe 

 thanks to Mr H. H. Brindley of St John's College, and to 

 First Lieutenant J. T. Saunders of Christ's College, for much 

 helpful criticism. 



We are grateful for the reception which has been accorded 

 to the second edition : we hope that the changes we have 

 alluded to may increase the usefulness of the book. 



A. E. S. 

 E. W. M. 



1st January, 1915. 



