PREFACE. V 



more restricted, or very rarely a more extended meaning 

 than its original proposer applied to it. If this was not 

 allowed, many new names must be added to the list of genera, 

 which is already so overburdened with synonyma. 



In those cases where the two sexes of the same species, 

 or any particular individual state or variety belonging to it, 

 have been differently named, the names belonging exclusively 

 to the state or individual described are placed after the refer- 

 ence to the specimens to which they apply. 



To determine with accuracy the names and synonyma of 

 the species, the various skeletons and other remains of Ce- 

 taceous animals in the museums of the College of Surgeons 

 of London and Edinburgh, of the Zoological Society, and of 

 the different local museums, especially those of Haslar, Nor- 

 wich, Bristol, Liverpool, c., and the various continental 

 museums of Paris, Leyden, Berlin, Vienna, and Frankfort, 

 have been personally examined, and in many cases the spe- 

 cimens contained in those museums have been sent to the 

 Museum, so that they could be actually compared with the 

 specimens in the Museum Collection. 



JOHN EDWARD GRAY. 

 June 1, 1850. 



