Image of: Physella
ADW: 060.rjb1.jpg
Caption
Physella
. Two species of the same genus. One species is darkly pigmented, while the other lacks pigment. But there are also other differences - in the internal anatomy and in small but consistent differences in the shells.
Contributors
Dr. John B. Burch, Ph.D.
(photographer, copyright holder), Mollusk Division, Museum of Zoology, University of Michigan
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