PREFACE. 



examples of Mediterranean Nudibranchs sent us by Professor Verany, of Nice. Along with 

 many other favours, we owe to our valued and lamented friend, Dr. Johnston, of Berwick, the 

 kind encouragement which first induced us to undertake this work, the completion of which, 

 alas ! he has not lived to witness. 



To mention all to whom we are under obligations would be to enumerate nearly every 

 living naturalist who has paid attention to the subject. The assistance we have received 

 from each is, we trust, duly acknowledged in its proper place. We may, however, be allowed 

 to particularise here the names of Professor Airman, of Dublin ; Mr. Cocks, of Falmouth ; 

 Dr. Gray, of the British Museum ; Mr. Price, of Birkenhead ; the Rev. David Landsborough, 

 junr., of Kilmarnock ; Mr. Barlee, of Exmouth ; and Mr. George Murray, of Burghead. To 

 our friend, Dr. Embleton, our thanks are especially due for the assistance he has given us in 

 the necessary anatomical investigations. With the advantage of his assistance, we feel greater 

 confidence in the result of our labours in this department than we should otherwise have done. 



In nothing has the lapse of time since the commencement of our task been more 

 forcibly impressed upon us than in the losses we have sustained by the hand of death during 

 its progress. Not only have we to lament the untimely decease of the three eminent 

 naturalists, Dr. Johnston, Professor Edward Forbes, and Mr. Thompson of Belfast, who were 

 appointed a sub-committee of the Ray Society, to see this work through the press, and who took 

 a friendly interest in its progress ; but two of the artists who have successively been employed 

 in it — Mrs. Holmes, who undertook the lithotinting of the earlier parts, and Mr. Wing, who 

 succeeded her with equal ability — are now also numbered with the dead. The later plates 

 have been executed by Mr. Ford, of the firm of Ford and West, in a manner that has met 

 with our entire approbation. The style has been changed from lithotint to lithography, we 

 think with advantage ; as the latter, in the hands of a competent artist, possesses the advan- 

 tage of greater certainty in the execution than can be attained by the former method. 



Newcastle-upon-Tyne, 

 Sept. 1855. 



