As : Diplodonta pilula Dall, 1881
Shell small, round, inflated, polished, with concentric sculpture of slightly raised sharpish ridges ; umbos smooth, polished, prominent, inflated ; margins not angulated, forming nearly a perfect circle, teeth indistinct; margin smooth ; epidermis if any thin and translucent. Lon. 2.6 ; alt. 2.6 ; diam. 2.6 mm.
Station 43, 339 fms., living.
This little shell resembles a homoeopathic pill as much as anything, ami, curiously enough, seems to be mature. The teeth are so indistinct that I feel a slight doubt as to whether it is a Diplodonta or not.

This little shell when submitted to higher powers, and especially when compared with the V. atlantica, was recognized as a Vesicomya. Its very minute size and the difficulty of opening it without breaking it led to its reference in the preliminary work to Diplodonta, while the doubt attending the reference was at the same time expressed. I am of the opinion that it is really a young specimen of the species afterward named atlantica by Mr. Smith, but I do not feel certain of it. Should it turn out to be so, I should prefer to waive my name in favor of Mr. Smith's, for the reason that there was not information enough in my description to enable any one to recognize it as a Vesicomya.