IXTRODUCTOUY EXPLANATION. 



The introduction to the first part of the ' jNIonograph of the Great OoHte Molhisca ' 

 contained an intimation that, with increasing knowledge of the testacea of the Cornbrash 

 and Forest Marble, it might eventually be desirable to give an additional monograph, or 

 an Appendix to that work. The materials which have latterly been placed at the disposal 

 of the writer are so considerable that he has been induced to endeavour to fulfil the 

 anticipatory announcement made in 1S50, and also to correct some errors, both textual 

 and typographical, which occur in the former Monograph. In the execution of his task 

 the writer begs thankfully to acknowledge the assistance he has received in the loan of 

 specimens from gentlemen whose names will be found mentioned in connexion with each 

 of the species illustrated, nor can he omit gratefully to mention the great advantages he 

 has derived from the constant opportunities that have been afforded to him of comparing 

 the Oolitic fossils of the southern counties with those of Yorkshire, contained in the very 

 extensive and choice collection of Mr. Leckenby, of this place. 



Scarborough; Septemler Cy, ISGl. 



