The Echinoid Directory

 Micrasterine spatangoids with:

• thin-shelled, ovate test with convex anterior;
• ethmolytic apical disc; genital plates often coalesced;
• peristome D-shaped and flush;
• labral plate mushroom-shaped; not extending beyond posterior of second ambulacral plate. Sternal plates symmetrical, fully tuberculate. Episternal plates paired; narrowing posteriorly with ambulacral plates 6-8 indenting;
• subanal fasciole generally present;
• aboral surface with small primary tubercles set amongst finer granules.

Miocene (Italy) to Recent; Indo-Pacific, Caribbean, and Atlantic.

The presence of a subanal fasciole and the indentation of the posterior interambulacrum behind the episternals by ambulacral plate 6 identify this group as belonging to the Micrasterina.

Mortensen, T. 1950. A monograph of the Echinoidea. V. Spatangoida 1. C. A. Reitzel, Copenhagen.