Byssonychia? sp. från Karmøy.
Abstract
Material: Cast of bivlved specimen and some impressions of the exterior. Diagnosis: Equivalved, laterally very unsymmetrical, form elliptical, height greater than length. Margo cardinalis, the hinge line, straight, somewhat longer than half the length of the mussel. Umbo anterial, small, acuminate, little elevated above the hinge line. A narrow but high pedal sinus is present. The valves very faintly convex, the width of each valve about 1\/10 the length. Posterial wing present. Straight radiating ribs as well externally as internally on the shell, increasing in strength outwards, 4 in one cm at the poster-oventral margin. Adductor scars unknown. The mantle line, partially appearing, is simple. Ligament area straight, possibly one postero-lateral tooth, perhaps more than one, were present, whether cardinal teeth were present unknown. Comparison and correlation: Ulrich (1897 p. 498) broke out Byssonychia with Amb.radiata Hall as the genotype from Hall's genus Ambonychia (Hall 1847, 1859). This is justified, but, as must here be pointed out, later students have not correctly referred to the original diagnosis nor to the external appearance of the genotype.