Vlll PREFACE. 



hail become the work of years. Mr. Clark had aban- 

 doned the field in which he had years ago laboured so 

 diligently and skilfully, though now, fortunately for 

 science, he has returned to it with renewed vigour and 

 enthusiasm. To all these gentlemen we offer our warmest 

 thanks for their most generous contributions of original 

 materials. The choicest specimens in Mr. Jeffreys' cabi- 

 net have been placed at our disposal for figuring, without 

 reserve, and the pencil of Mr. Alder has, in many in- 

 stances, embellished our illustrations with figures exceed- 

 ingly precious, since from no other source could they bo 

 procured. 



Our valued and lamented friend, the late William 

 Thompson, of Belfast, who had devoted years of study to 

 the British Mollusks, aided us, as long as he lived, with 

 every possible assistance that lay in his power. In all 

 that concerns the distribution of Irish species, his hand 

 may be traced, and advice, notes and specimens were con- 

 stantly coming from him for our use. For many of the 

 details that we are enabled to give respecting the distri- 

 bution and range of the species described, we owe the 

 fullest thanks to Mr. M'Andrew, of Liverpool, who, with 

 a zeal too rarely imitated, has for years spared neither 

 expense nor labour in searching out marine animals in 

 their deepest recesses, a work, often-times, of no small risk 

 and danger. 



The veteran conchologist of Scarborough, Mr. William 

 Bean, has liberally aided us in numerous instances. The 

 precious cabinets of Mr. Cuming have been opened to us 

 most freely for consultation. Specimens of peculiar value 

 and interest, have been confided to us by Sir Walter Tre- 

 velyan, Dr. Eobert Ball, Dr. Farran, Mr. Albany Han- 

 cock, Mr. Warren of Dublin, and Mr. Couch. Wo owe 



