Michael Reagin discussed fossil Xenophora in the southeastern United
States. Here is a summary of the messages that I sent to Tom Eichorst in
New Mexico, which may be of more general interest (and are definitely on
shells, not soup).
 
Xenophora leprosa (Morton, 1834) shows up occasionally in the Upper
Cretaceous Prairie Bluff Chalk of Alabama and Mississippi. Unfortunately,
all of these specimens are steinkerns, that is, the shell is dissolved away
and only the sediment filling the former living space is preserved. The
steinkerns are intriguingly bumpy, preserving some of the shape of the
shells that were attached to the exterior, but in no great detail. Sohl
(1960, p. 96-97, pl. 10, figs. 19, 23-27) gave a good description of them.
 
Well-preserved specimens of X. leprosa are extremely rare; a very few have
been found in the Upper Cretaceous Coon Creek Formation of Tennessee (Sohl,
1960).
 
Palmer and Brann's catalog of Paleocene and Eocene mollusks from the
eastern U.S. includes a few species of Xenophora. I've never collected any
Xenophora in the Lower Tertiary of Alabama; they may be rather rare in this
interval:
 
X. humilis (Conrad, 1848), Upper Eocene to Oligocene
X. lapiferens Whitfield, 1892, Middle Eocene
X. reclusa (Conrad in Wailes, 1854), Upper Eocene
Xenophora spp. indet., Paleocene to upper Eocene
 
If they're so rare, then why were they spotted so early? All I can say is,
(1) Conrad had a great eye (and wasn't afraid to base a new species on a
unique specimen), and (2) It helps to be the first collector on the scene.
 
Andrew K. Rindsberg
Geological Survey of Alabama
Tuscaloosa, Alabama, USA
 
References
 
Palmer, K. V. W., and Brann, D. C., 1965-66, Catalogue of the Paleocene and
Eocene Mollusca of the Southern and Eastern United States: Bulletins of
American Paleontology, v. 48, no. 218, 2 v., 1057 p., 5 pl. Published by
the Paleontological Research Institution; may still be in print. Held by
many university libraries.
 
Sohl, Norman F., 1960, Archeogastropoda, Mesogastropoda and stratigraphy of
the Ripley, Owl Creek, and Prairie Bluff formations: U.S. Geological
Survey, Professional Paper 331-A, p. i-iv, 1-151, pl. 1-18. Possibly still
in print.