EDITORIAL NOTE. 
Tae collection of Astzrorpea is one of the most important made during the 
voyage of the Challenger. The late Sir C. Wyville Thomson paid con- 
siderable attention to these organisms, and at one time had the intention 
of describing the new species discovered during the Expedition; with this 
end in view, indeed, he had a few of the specimens figured and_litho- 
graphed. 
Eventually, however, the whole collections were handed over to Mr. W. 
Percy Sladen for examination and description. The result of Mr. Sladen’s 
work, extending over many years, is now presented in this magnificent 
Report, which forms Part LI. and Volume XXX. of the Zoological series 
of Reports, the text and plates being bound up in separate parts. 
Not only on account of the large number of forms, but also on account 
of their representative character, the Challenger collection is unquestion- 
ably the most important contribution to this group of animals that has 
ever been made. 
In the Report, supplementary to the treatment of the Challenger 
material, a compact account of the whole group has been aimed at. Thus 
(1) under each family an account of all the genera included therein, 
whether Challenger or not, has been given, and where necessary the 
grounds on which the classification has been adopted are discussed; (2) 
under each genus there is a statement of all the known species which are 
recognised as belonging to that genus, with an account of their geo- 
graphical distribution: this presents a compact idea of the composition and 
distribution of each genus ; (3) a complete list of all the known species of 
