Engel, H. 1972. Phymosoma maastrichtensis spec. nov., a fossil echinoid from the Cretaceous of Maastricht (Echinacea, Phymosomatoida, Phymosomatidae). Zoologische Mededelingen 47, 540-544.
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Engel, H.
1972
Phymosoma maastrichtensis spec. nov., a fossil echinoid from the Cretaceous of Maastricht