INTRODUCTION. 



Iif the present Catalogue I have endeavoured, as far as possible, to 

 follow in the lines laid down by Professor "W. H. Mower 1 in respect 

 to the nomenclature of species and genera, and in regard to general 

 systematic arrangement. A larger number of synonyms are, how- 

 ever, introduced, because in the case of fossils there is at present, 

 unfortunately, but little uniformity in nomenclature, and the same 

 species is still quoted by different writers under different designa- 

 tions. In the case of the less frequently employed synonyms 

 references are not always given. For each generic and specific 

 name adopted I have given, as far as possible, the place and date of 

 its first occurrence, and in many of the less perfectly known forms 

 references are added to figures or full descriptions. Great care has 

 been taken in endeavouring to find the proper name of each genug 

 and species. 



In regard to systematic arrangement, I have endeavoured to so 

 modify that adopted by Professor Flower as to make it include the 

 host of extinct forms which are here dealt with, as it would be 

 inconvenient to be continually referring groups to an Incerta sedes. 



In the case of well-known forms very frequently no specific or 

 generic characters are given ; but in instances where there are a 

 number of closely allied genera, or a large number of species be- 

 longing to one genus, and distinguished by characters which are 

 not always readily apparent, I have frequently added a short notice 

 of some of the more important generic and specific characters which 

 are applicable to fossils. These characters are more fully given in 

 the case of imperfectly known forms ; and in some instances indi- 

 vidual specimens which are of more than ordinary interest are more 

 or less fully described. Species which still exist are indicated by 

 their names being printed in Old-English characters. 



1 Catalogue of Specimens of Vertebrated Animals in the Museum of the 

 Royal College of Surgeons, part ii. (1884). 



