The Echinoid Directory

Planilampas Mortensen, 1948, p. 297

Diagnostic Features
  • Test of medium size, ovoid in outline, aboral surface low vaulted, adoral surface relative flat, slightly sunken towards the peristome.
  • Apical disc slightly anterior; monobasal, with four gonopores.
  • Petals narrow, slightly bowed, open distally. Pore-pairs small and circular, pores in the outer series being very slightly larger; nonconjugate to subconjugate; the two columns in each petal of very unequal lengths, especially in the posterior paired petals; pores beneath petals single.
  • Peristome subcentral, pentagonal, transverse, wider than long.
  • Periproct inframarginal and transverse; not sunken.
  • Phyllodes short but strongly developed, single pored, with two or three series in each half ambulacrum, plus scattered pores in between.
  • Bourrelets weakly developed, forming a distinct well leading to the peristome opening.
  • Buccal pores present.
  • Tubercles the same size adorally as adapically.
  • Narrow, naked, granular zone in interambulacrum 5.
Middle Eocene (Lutetian) to Recent, worldwide distribution.
Name gender feminine
Echinolampas sternopatela Agassiz & Clark, 1907, p. 130; by original designation.
Species Included
  • Mortensen (1948) included just two species when erecting this genus:
  • E. (Planilampas) keiensis (Mortensen, 1948); Recent, Kei Islands, Indonesia
  • E. (Planilampas) sternopetala Agassiz & Clark, 1907; Recent, Japan
Classification and/or Status

Irregularia; Cassiduloida; Echinolampadidae.

Subjective junior synonym of Echinolampas (Miolampas)  Pomel, 1883.


Echinolampas (Planilampas) can be differentiated from Echinolampas (Echinolampas) by the very marked inequality in the length of the two series of pore-pairs in each petal. In Echinolampas (Planilampas) the shorter pore-series typically measures between half to two-thirds of the length of the longer pore-series; while in Echinolampas (Echiolampas) the shorter pore-series measures at least four-fifths of the length of the longer pores-series in that petal. Mortensen (1948) further differentiated it on its flat oral surface. However, the oral surface is not much flatter than that of other Echinolampas species. As petal asymmetry is also very pronounced in Pomel's Miolampas, Planilampas is treated as a junior synonym of this taxon.

T. Mortensen. 1948. A monograph of the Echinoidea: 4 (1): Holectypoida, Cassiduloida. Reitzel, Copenhagen, 363 pp., 14 pls.

M. Shigei. 1986. The sea urchins of Sagami Bay. Biological Laboratory, Imperial Household, Maruzen Co. Ltd, Japan, 173 pp. 126 pls