Parallelodon carbonarius (Cox 1857) is a bivalve with distribution from the older Pottsville Group to the younger Conemaugh Group in Ohio and Pennsylvania. This is the first specimen of this species that I have found in over three years of searching through the Brush Creek limestone and the Pine Creek limestone. The fossil was recovered in the limestone proper. It measures 45 mm in length. Morningstar (1922) wrote that “It is characterized by surface sculpture of prominent, regular, radiating plications which become considerably larger and stronger on the flattened posterior portion below the hinge line”.

There are four good figures (Sturgeon et al., 1979, Plate 3, Fig. 4-8) to observe in the 1979 book Pennsylvanian Marine Bivalvia and Rostroconchia of Ohio. They are the same as this specimen and the species identification is correct. The original by Cox, Arca Carbonaria is missing the lithographed plates in the online versions, so I could not find the original figure yet.

Parallelodon carbonarius with metric scale
Figure 1.—Parallelodon carbonarius (Cox, 1857). Specimen ID: CG-0310
Parallelodon carbonarius
Figure 2.—Parallelodon carbonarius (Cox, 1857). Specimen ID: CG-0310