PREFACE. 



This short preface is intended both as an explanatory notice and as a 

 dedication. Without the aid of my friend Mr. M'Andrew, the following 

 Monograph could not have been drawn up. The mass of the materials 

 employed in its construction was the produce of several delightful scientific 

 cruises, when I accompanied him in his Yacht, the Osprey. Nine 

 years ago this history was commenced : were it not for the ardent friend 

 of science, whose name I wish to associate with my work, as many more 

 would be required for its completion. Even now, I can offer only an 

 outline of a most curious and interesting, though neglected, department of 

 British Zoology. The greater part of the matter in this essay is new. With 

 one exception — kindly communicated by Mr. Alder — every species has been 

 examined by myself. Every figure is original. Any defects in the 

 engravings must be laid to my charge ; their merits are due to my friends 

 Mr. W. Baily, and Mr. C. R. Bone, for whose exertions I have to return 

 many thanks. 



Edward Forbes. 



London; June 'ih, 1848. 



