The Nautilus. Vol. XXXI, No. 2, October 1917 / A Quarterly Journal Devoted to the Interests of Conchologists

by Various

2. Fusconaia barnesiana bigbyensis (Lea) 1841.

U. bigbyensis Lea, ’41. U. estabrookianus Lea, ’45. U. fassinans Lea, ’68. Pleurobema fassinans rhomboidea Simpson, ’00.

The most frequent form is fassinans rhomboidea (topotypes examined), with rays poorly developed. U. bigbyensis has more distinct rays; U. estabrookianus (topotypes examined) is an old, overgrown form, without rays; U. fassinans is founded upon an individual (type examined, also topotypes), which is exceptionally elongated, without rays.