The Echinoid Directory

• Test subpentagonal; as wide as long or slightly elongate; depressed, ambitus low; oral surface depressed towards peristome
• Apical central, opening large; plating lost. Disc not elongate (distance separating anterior and posterior paired ambulacra not large). Periproct opening into a well-developed anal sulcus that extends more or less to the posterior ambitus.
• Ambulacra not petaloid aborally; pore-pairs small, uniserial, decreasing slightly in size towards ambitus. Uniserial on oral surface with no crowding; all plates simple, but becoming organized into triads towards the peristome.
• Peristome large and depressed with inturned walls; central; oblique with long axis running from interambulacrum 3 to ambulacrum I. Possibly with a couple of pairs of shallow buccal notches.
• Oral tubercles large and with radial directed areole enlargement. Aboral tubercles slightly smaller, uniform and set in a dense granulation.

Jurassic (? Pliensbachian, Toarcian-Bajocian), Europe, North Africa.

Hyboclypus nodoti Cotteau, 1859, p. 52, by original designation.

• M. nodoti (Cotteau, 1859); Bathonian, France.
• M. microstoma (Lambert, 1933); Toarcian, Morocco
• ? M. hebbriensis Lambert (1933); Pleinsbachian, Morocco

Stem group irregular.

Monotypic.

Distinguished from Galeropygus by the complete absence of pore crowding adorally and by its large oblique peristome. Distinguished from Pygaster by its anal sulcus.

Pomel, A. Classification méthodique et genera des Échinides vivante et fossiles. Thèses présentées a la Faculté des Sciences de Paris pour obtenir le Grade de Docteur ès Sciences Naturelles, 503, 131 pp. Aldolphe Jourdan, Alger.