57-13 



Proceedings of the American Academy of Arts and Sciences. 



Vol. 57. No. 13.— June, 1922. 



CONTRIBUTIONS FROM THE BERMUDA BIOLOGICAL STATION 



FOR RESEARCH. No. 138. 



THE ECHINODERMS OF THE CHALLENGER BANK, 



BERMUDA. 



By Hubert Lyman Clark, 



With One Platk. 



