Reports on the dredging operations off the west coast of Central America to the Galapagos, to the west coast of Mexico, and in the Gulf of California, in steamer "Albatross," &c. xxiii. Preliminary Report on the Echini. Bulletin of the Museum at Harvard College, xxxii(No. 5) 1898: pp. 71-86. 73 [Zoological Record Volume 35]