Left-valve and dorsal views
General abundance:
Common
Viewer Comments:
This species is characterized by widely separated
large
concentric ribs, without fine concentric laminae between
the coarse ribs. On this specimen, small nodes can be
seen along the lower margin of the valve, which appear
to be denticles on the interior margin of the other valve.
This indicates that the two valves are slightly displaced,
to show the interior edge of the underlying valve.
Dr. Tom Yancey
The A. varica appears to have
some serpulid worm tube
attached to them. The A. concentrica
appears to be free
of commensals. It might be an interesting study to see
if one is wormy and the other worm free---that may
have as much meaning as morphologic features.
Dr. Roger Pabian
References:
S. O. Bird, 1968, A pelecypod fauna from the Gaptank
Formation (Pennsylvanian) West Texas; Bulletins of
American Paleontology, no. 240, p.163-167. Although
the report is for a Texas locality, the species descriptions
include good discussion of species from the midcontinent
region.
The above reference supplied by Dr. Tom Yancey
Fossils of Ohio, Bulletin 70,
Ohio Division of Geological Survey, 1996.
Pages 148-149 (fig. 14 and 15)
A Field Guide to Fossils of Texas
Second Edition by Charles Finsley
Page 66, Plate 51, Photo 148
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