The Echinoid Directory

• Test flattened below, domed above.
• Apical disc small; dicyclic; plates firmly bound to corona. Ocular pores double. Periproct oblique, covered by four large plates forming an anal valve. No tubercles on plates, but with distinct epistromal ornament.
• Ambulacra more or less straight; plating trigeminate throughout; pore-pairs uniserial aborally with suckerless tube-feet, the pore-pairs elongate and subconjugate. Pore-pairs expanded into a strong phyllodes adorally, with rounded pore-pairs and strong, suckered tube feet.
• Plate compounding arbaciid-style with the upper and lower elements reduced to demiplates. On oral surface triads become coalesced to form more complex compound plates. A single primary tubercle to each compound plate.
• Interambulacral plates wide; with 3 subequal primary tubercles forming a horizontal row on plates at the ambitus. Only the outer series continues adapically, leaving a wide, bare interradial zone covered only in fine epistroma.
• Primary tubercles imperforate and non-crenulate, with relatively large mamelon and poorly defined platform. On oral surface forming en-chevron pattern.
• Peristome subpentagonal and very large (more than half test diameter), crenulated, with very shallow buccal notches and a perradial notch. Smooth tags extend adradially from the buccal notches along the proximal interambulacral plates.
• Basicoronal interambulacral plate present.
• Peristomial membrane rather naked, except for 10 buccal plates.
• Perignathic girdle with tall and slender auricles that are generally fused perradially.
• Primary spines moderately long (usually a little less than the test diameter); ambital and adapical spines distally pointed, without cortex. oral spines ending in a small cap of glassy stereom (cortex).
• A single sphaeridium situated close to the peristome in a perradial pit.

Miocene to Recent, western Atlantic seaboard and Caribbean.

Echinus punctulatus Lamarck, 1816, p. 363, by monotypy.

• Lambert & Thiery (1910) included four other species, all extant.

Euechinoidea, Echinacea, Arbacioida, Arbaciidae

Subjective junior synonym of Arbacia Gray

Agassiz (1841) created this genus for punctulatus, separating it from lixula by its naked interradial bands. Although kept as distinct by Lambert & Thiery (1910), it has almost universally been treated as a synonym of Arbacia by subsequent authors.

Agassiz, L. 1841. Observations sur les progress récens de l’histoire naturelle des echinoderms. Monographie d’Échinodermes vivans et fossiles. Seconde Monographie, première section, 20 pp. Petitpierre, Neuchâtel.

Mortensen, T. 1935. A monograph of the Echinoidea II. Bothriocidaroida, Melonechinoida, Lepidocentroida and Stirodonta. C. A. Reitzel, Copenhagen.