BICONCAVA Hamaoui, 1965
Type species: Biconcava bentori Hamaoui, 1965 (*1381), p. 14; OD(M).
Biconcava Hamaoui, 1965 ( *1381), p. 14 (available, ICZN Art. 13 (c)); see also Hamaoui and Saint-Marc, 1970 (*1386), p. 298.
Biconcava Hamaoui, in Arkin and Braun. 1965 (*69), p. 7, 9. (name not available, ICZN Art. 13 (a) (i), no description).
Test free, planispirally enrolled, partially evolute, biumbilicate, periphery subacute, up to twenty-four chambers in the final whorl, about three and a half whorls in the adult, sutures elevated, slightly curved; wall calcareous, microgranular, imperforate; aperture in the early stage an interiomarginal arch with extension up the apertural face, later areal in a median groove that extends up the apertural face. U. Cretaceous (Cenomanian); Israel; Lebanon; Iran; Italy.
Remarks: In placing Biconcava in the Nezzazatidae, Hamaoui and Saint-Marc (1970, *1386, p. 301) refer to a rudimentary internal toothplate; this structure does not appear evident in the illustrated sections, hence the genus is here transferred to the Mayncinidae. It is closest in appearance to Daxia but differs in being more evolute and in the aperture located in a vertical groove in the apertural face.
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