Shell inequilateral, inflated. Posterior end subrostrate to rounded, usually slightly gaping. Periostracum iridescent, adherent. Sculpture usually absent, but weak commarginal lirae or growth lines may be present. Escutcheon and lunule obscure. Hinge plate weak, with taxodont teeth in two series. Ligament amphidetic, with small external portion and a resilium in oblique, broad resilifer. Pallial sinus small. Siphon an entire, thick, closed tube.
The genus is named from the diminutive of the genus Yoldia, to which the species have a superficial resemblance; it is of feminine gender. Their small size and offshore habitat make them uncommon in collections. It is likely that species referable to other genera have been included in Yoldiella because it is easy to confuse immature specimens. We limit Yoldiella to those forms with an elongate, amphidetic ligament, with an internal section, obscure or absent escutcheon and lunule. and a small pallial sinus. Recorded back to the late Cretaceous.
We find at least some species of Yoldiella, of which we have a substantial number of specimens, arc quite variable in shape, and this has prompted us to synonymize a number of taxa. This suggests that a much more careful study of all of the taxa is required before one can be confident that a sound classification is in hand.