The Echinoid Directory

• Test wheel-shaped, flattened below and above.
• Apical disc small, pentagonal; dicyclic.
• Ambulacra trigeminate; plate compounding acrosaleniid with two elements overlapped by a primary tubercle and a third simple element. All elements reach the perradial suture. Pore-pairs uniserially arranged. Adapical plates simple and without well developed primary tubercles.
  
• Interambulacral plates a little wider than tall, with singlel primary tubercle occupying much of the plate. Secondary tubercles around edges of the plate.
  
• Ambulacral and interambulacral tubercles of similar size; iPrimary tubercles imperforate and non-crenulate; mamelon rather massive.
• No aboral naked interradial zone.
• Peristome large, a little sunken; buccal notches small but sharp.
• Spines and lantern unknown; no primordial interambulacral plate.

Middle Jurassic, USA.

Parastomechinus brightoni Philip, 1963, p. 1112, by original designation (type destroyed).

• Only the type species.

Acroechinoidea, Carinacea, Pseudodiadematidae.

Monotypic; subjective junior synonym of Hessotiara Pomel, 1883.

Philip, G. 1963. A new regular echinoid from the Jurassic of Wyoming, USA. Journal of Paleontology 37, 1110-1115.