. Bulletin of the Natural Histort Museum. Geology series. 106 SMITH ETAL. mens are, however, too poorly preserved to form the basis for formally erecting a new species name. Order HOLASTEROIDA Durham & Melville, 1957 Diagnosis. Irregular echinoids with meridosternous or orthostemous plastron, paired ambulacra flush on test; apical disc elongate with one or both ocular plates inserted between anterior and posterior pairs of genital plates. Family HOLASTERIDAE Pictet, 1857 Genus OFFASTER L. Agassiz, 1836 Diagnosis. Small holasteroids with flat to slightly convex base and vaulted upper s
. Bulletin of the Natural Histort Museum. Geology series. 106 SMITH ETAL. mens are, however, too poorly preserved to form the basis for formally erecting a new species name. Order HOLASTEROIDA Durham & Melville, 1957 Diagnosis. Irregular echinoids with meridosternous or orthostemous plastron, paired ambulacra flush on test; apical disc elongate with one or both ocular plates inserted between anterior and posterior pairs of genital plates. Family HOLASTERIDAE Pictet, 1857 Genus OFFASTER L. Agassiz, 1836 Diagnosis. Small holasteroids with flat to slightly convex base and vaulted upper surface. Apical disc with four gonopores. Frontal groove absent aborally, slightly depressed at ambitus and subambitally, at least in small individuals. Peristome oval to D- shaped; facing downwards, with little or no labral projection. Plastron meridosternous with first two to three plates uniserially arranged. Periproct on posterior face. Marginal fasciole present, at least in juvenile stages; possibly absent in larger individuals. Offaster leymeriei CottesLU, 1887 PI. 4, figs 10-13; Figs 14, 15 1887b Offaster Leymeriei Cotteau: 661, pi. 19, figs 14, 15, pi. 20, figs 1-3. 71927 Ojfaster dallonii Lambert: 43, pi. 3, figs 12-15. 1992 Ojfaster dallonii Gallemi: 257, photo 14. 1996 Ojfaster dallonii Wilmsen et al.: fig. 7. Diagnosis. Test up to 30 mm in length; width ca. 80-85% length; height ca. 65% of length. Ovate in outline; specimens larger than about 15 mm with convex anterior, smaller individuals with slight anterior sulcus developed from ambitus adorally. Peristome moder- ately large, oval, 15% test length from the anterior. Periproct large, occupying the upper part of the posterior face, which slopes very slightly inwards so that the periproct is just visible from below but not from above. Plastron plating meridosternous. Tuberculation relatively fine, with no primaries differentiated aborally. Small indi- viduals show a clear marginal fasciole around the posterior margin
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Keywords: ., bh, bookcentury1900, bookcollectionbiodiversity, bookleafnumber62
