ADVERTISEMENT. 



As the philosophical study of these animals is yet in a state of progression, and has 

 lately received much attention from physiologists, the authors have also determined to defer 

 their general views on the Order till near the completion of the work, so that they may be 

 brought up to the knowledge then attained. 



In the meantime they have given a Synopsis of the genera into which the British species 

 may be divided, with a list of the species at present known. This will allow the reader at 

 once to refer each species, as it appears, to its proper place, and to understand the charac- 

 ters of those genera, the detailed account of which may not appear until a subsequent part 

 of the work. This synopsis will afterwards be superseded by a more complete systematic 

 arrangement. 



The authors have pleasure in stating that, in making out the anatomical details, they 

 have had the able assistance of their friend Dr. Dents Embleton, Lecturer on Anatomy in 

 the Newcastle School of Medicine. The plates are accurate transcripts of their original 

 drawings. They have been executed by Mrs. Holmes, an accomplished artist in Lithotint, 

 an invention of Mr. Hullmandel, admirably adapted for pourtraying the delicacy and 

 beauty of these fragile inhabitants of the sea. 



Newcastle'; June 1845. 



