A. rubens. The ruddy Anodonta.
Species oval, hinge arched, without trace of auricula or ear.
A. trapezialis. The trapezium Anodonta. Pl. [11], fig. 3. Species oval or rounded, auriculated on both sides the summit.
4. Iridina. One species.
A very rare shell, separated from the Anodonta on account of the hinge being attenuated in the middle, and having small tubercles distributed along its length. The substance is thicker and more solid than the Anodonta, and of a brilliant rose-coloured pearly hue; it is found in the rivers of warm countries.
Shell equivalve, inequilateral, transverse, with small apices; recurved, but nearly erect; not auriculated; hinge very long, linear, crenulated through all its length; ligament external and marginal; two well-marked muscular impressions.
I. exotica. The exotic Iridina.
The only species of this genus answering to the above description.