Two exceptionally well-preserved specimens of Vintonia doris, a new demosponge, are found in concretions within the Mississippian Fayetteville Shale in northern Arkansas in an association which suggests that the sponges were part of the diet of cephalopods. The species is a slightly nodose form that has a deep, broad open spongocoel and a large osculum. Relatively thin walls of the sponge are clearly separable into an organic-rich ectosomal layer and a more open vesicular choanosomal layer. Depressions in the choanosome, opening into the spongocoel, are interpreted as flagellate chambers. Two buds(?) are present in one section of the type specimen. Vintonia is placed in a new family, the Vintoniidae, within the order Keratosida. The new family is distinguished by a well-defined ectosome and large, sack-shaped flagellate chambers, which empty into the large simple spongocoel.