Scientia Sinica

No. 1 WANG: NEW SPECIES OF BRACHIOPODS [I] 165

America. There can be no doubt that Mimella formosa is the first record of

this genus in China and Eastern Asia.

Important differences between Mimella formosa and all other species of the genus are to be found both inside and outside.. Externally, our form is characterized by its short, normally apsacline ventral interarea, swollen umbonal region and strongly incurved beak, with the. greatest convexity of the shell around the middle and a very narrow fissure between the interareas. The American species, on the other hand, is distinct by virture of its highly erect ventral umbo and much higher interarea. Internally, the diductor scars of Mimella formosa are conspicuously shorter than those of the American species.

Genus Martellia Wirth 1936 Martellia ichangensis Wang (sp. nov.) : (EIS GC; Figs: 15) 1936 Martellia giraldu, Wirth: Palzont. Zeit. B. 18, T. 20, Figs. 1-19.

Shell medium in size; anterior margin extended; subpentagonal in outline; hinge-line straight, usually less than the greatest width at the middle; unequally biconvex in lateral profile; the ventral valve deeper than the dorsal valve, hemipyramidal; cardinal extremities rectangular or obtusely acute; lateral margins rounded; anterior commissure slightly uniplicate. Ventral interarea conspicuously long, strongly apsacline; delthyrium narrow and long, covered by a highly arched pseudodeltidium, without apical perforation. Surface multicostellate, costellae fine and even, about 20 costellae in 5 millimetres at front of the shell; surface undulated by variations of growth.

Ventral exterior: Strongly convex in lateral profile, with the greatest convexity at the postero-median part of the valve, anterior profile broadly and evenly convex; interarea flat, strongly apsacline, ornamented by horizontal striations; umbo flattened; beak minute, obtuse, apical angle being of about 130 degrees; front half of the valve marked by a faint, shallow sulcus.

Dorsal exterior: Lateral profile flatly and moderately convex; umbo depressed; a narrow and low fold originating from the middle of the valve and extending to the anterior margin; beak minute, inconspicuous; interarea short, strongly anacline; notothyrium wide, closed completely by a horizontal chilidial plate.

Dimensions (mm): Length 12.2; width 13.0; thickness 5.4; hinge-width 11.8. :

Holotype, 1.P.A.S. 8003.

Horizon and locality: Neichia Series, Middle Ordovician; about one mile