Vein laid open, showing it's valves.

Vein and Valves

Vein laid open, showing it's valves.

"Waldheimia flavescens. Interior of ventral valve. f, foramen; d, deltidium; t, teeth; a, adductor impressions; c, divaricator; d, accessory divaricators; b, ventral adjustor; b', peduncular muscle." — Encyclopedia Britanica, 1893

Ventral Valve

"Waldheimia flavescens. Interior of ventral valve. f, foramen; d, deltidium; t, teeth; a, adductor impressions;…