CONTENTS. 



p. 



Introduetion 5 



List of Memoirs referred to 6 



Critique of the Priapulida and Echiurida, known to inhabit the Northern and Arctic Seas, and 



of the questionable genera Saccosoma and Epithetosoina 8 



Sub-Order Priapulida 12 



Sub-Order Echiurida 13 



Sub-Order Saccosomatida 14 



Account of the Species 15 



Priapulus caudatus (Lam.) 15 



Priapulus bicaudatus (Danielssen) 18 



Halicryptus spinulosus v. Sieb 19 



Echiurus Pallasii Guérin Méneville 22 



Hamingia arctica Danielssen and Koren 23 



Bonellia viridis Rolando 23 



Saccosoma vitreum Danielssen and Koren 24 



Explanation of the Plates 25 



