E. aucklandica is an aquatic bivalve mollusc in the family Unionidae, the river mussels.

Shell long, rhomboid, compressed or subcompressed, inequilateral; beaks subcompressed, pointed, their sculpture apparently a few irregular lachrymose nodules arranged in a somewhat radial pattern; surface with uneven growth lines and impressed rest marks, sculptured throughout with lachrymose nodules which are often V-shaped, those along the upper part of the low posterior ridge slightly knobbed; epidermis dark olive green, clouded with lighter green, rather dull; pseudo-cardinals small, subcompressed, granulose, two in each valve ; laterals straight, two in the left valve, one in the right; muscle scars small, shallow and irregular; nacre bluish,

lurid purple near and in the beak cavities, thicker in front.The length of the shell is 62–81 mm.

[3][4] Echyridella aucklandica is found in two separate locations, Southland and the lower North Island.

[4] Like other unionids, E. aucklandica has a complex life-cycle characterised by a parasitic larval stage called glochidia that require a fish host to metamorphose into juveniles.