More than 3 arm-spines which (except for the 3 inner ones) are modified as simple hooklets. Disc and arms covered above by naked skin. . . . Asteronyx Mueller & Troschel, 1842.

*loveni M. & T., 1842. North circum-polar. 100 fms.

Three (rarely 2) arm-spines, never hooked; disc covered above and below by thin, imbricating scales, especially well-developed at the margin. . . . Astrodia Verrill, 1899.

*tenuispina Verrill, 1899. N. Atlantic. 2,000 fms.