Trigoniidae

OBS: [Les Lamellibranches de la] famille des Trigoniidae (...) [ont une] coquille nacrée, inéquilatérale, [le] bord antérieur [est] généralement arrondi, beaucoup moins développé que le postérieur qui est plus ou moins tronqué et anguleux. [La] charnière [est] faite généralement de deux dents cardinales divergentes sur la valve droite et de une, deux ou trois dents cardinales divergentes sur la valve gauche; [le] ligament est externe; [ils ont] deux impressions musculaires; [et une] empreinte palléale entière.

OBS: [Bivalves of the Family Trigoniidae have shells that are] highly variable in shape and ornament; [the] umbones [are] most commonly opisthogyrous, but orthogyrous or prosogyrous in a few groups; [an] escutcheon [is] usually present; [the] area and flank [are] differentiated and differently ornamented in most genera; [the] flank ornament [is] generally concentric or oblique, but radial in some forms; [the] median tooth of [the] left valve [is] broad, grooved, strongly concave to deeply emarginate below; [the] posterior left [is] weak or obscure, marginal; [the] anterior left [is] of moderate strength; [the] right valve (...) [has] two subequal and more or less symmetrically divergent teeth not borne on [a] hinge plate, and (...) [a] very obscure anterior marginal tooth in some species; [the] two main teeth of [the] right valve and [the] sides of [the] left valve teeth against which they fit bear strong transverse ridges (...); [the] anterior myophorous buttresses [are] well developed; [the] pallial line [is] entire; Recent forms [are] filibranchiate; mantle lobes [are] free; [the bivalves are] nonbyssiferous. ""M.Trias.-Rec.""