"<em>A</em>, part of a vein laid open, with two pairs of valves; <em>B</em>, longitudinal section of a vein, showing the valves closed." &mdash; Blaisedell, 1904

Vein

"A, part of a vein laid open, with two pairs of valves; B, longitudinal section of…

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." &mdash; Encyclopedia Britanica, 1893

Ventral Valve

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