Comprehensive DescriptionRead full entry
“Genus Maorithyas nov.
Shell of moderate size, thin, globose, endentulous, sulcate posteriorly, beaks prosogyrous, ligament opisthodetic, chiefly internal, but visible from without, bounded by a narrow escutcheon. Hinge plate thin, shallowly excavate behind, to accommodate the ligament. Lunules well-defined. Fine radial threads on interior of shell, exterior with concentric sculpture.
Type: M. marama, n.sp.
Because of its sulcation, thin shell, and resemblance in hinge characters to Genaxinus, Maorithyas is here located in the Thyasiridae. There are a number of similarities with Cavatidens Iredale, described as an endentulous Lucinid for the shells recorded as “Thyasira” [sic] globose Forskal,” but Cavatidens has a straighter dorsal margin, more distinct muscle impressions, is only faintly sulcate, and furthermore is described by Cotton and Godfrey, 1938, p. 199, as opisthogyrate and with a wholly anterior ligament. Why Cotton and Godfrey (1938) and Iredale (1930) orient Thyasirids so as to make the sulci and ligament anterior and the beaks opisthogyrous is not clear. I have followed Dall, Suter and others in orienting these shells.”
(Fleming, 1950: 253)