Trachydomia nodosa (Meek & Worthen, 1861)

  
Trachydomia nodosa (Meek & Worthen, 1861)

General abundance:  Common at the limestone shale boundary

Special thanks to Dr. Tom Yancey for the identification
and the refernces.

This is Trachydomia nodosa (Meek & Worthen, 1861). This species
is illustrated in Knight (1933) and is listed in Yochelson (1967). There
is a partly developed shoulder on the upper part of the whorl that
does not have nodes on the adult portion of the shell. The large
coarse nodes on the shell are characteristic and they are formed
along the growth lines, but on the earlier formed parts of the shell
there are rows of nodes roughly aligned at an angle to the growth
lines. This species is of special interest because it is the type
species for the genus Trachydomia. Knight list the name as
Trachydoma, but Yochelson (1967) and the gastropod Treatise
use the correct spelling, Trachydomia.

Dr. Tom Yancey

References:

Knight, 1933, The gastropods of the St. Louis, Missouri,
Pennsylvanian outlier: 6, The Neritidae; Journal of Paleontology,
v. 7, p. 359-392

Yochelson, 1967, A bibliographic index of North American late
Paleozoic Hyolitha, Amphineura, Scaphopoda and Gastropoda;
U. S. Geological Survey Bulletin 1210, 271 pages.

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