Jesionek-Szymańska, W. 1970. On a new pygasterid (Echinoidea) from the Jurassic (Middle Lias) of Nevada, U. S. A. Acta Palaeontologica Polonica 15, 411-419.
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Jesionek-Szymańskaevada, W. N.; A, U. S.
1970
On a new pygasterid (Echinoidea) from the Jurassic (Middle Lias) of
Acta Palaeontologica Polonica
15: 411-419
Publication
from Kier & Lawson (1978)
Plesiechinus hawkinsi n. sp. from the Middle Lias of Nevada, U.S.A., the oldest and most primitive representative of an irregular echinoid family of the Pygasteridae Lambert, 1900, displays a "regular" apical system with genital 5 perforate. Crenulate tUb