Abstract

Ninety-one specimens of Pentremites Say from the Mississippian Chesterian display color patterns. The darker color patterns represent a thin veneer of pigmented calcite which is barely visible on a polished surface or thin section, but which can be removed with dilute hydrochloric acid. Preservation appears to be best in specimens from shallow marine clays and shales. The patterns represent four color patterns, each consisting of different shades of calcite, and ranging in color from tan to black. Color patterns generally, but not always, cross growth lines. Type 1 has arched chevron patterns on the deltoids, horizontal lines on the radials, and triangular bands on the basals. Type 2 has darkened deltoids or concave chevrons on the deltoids and darkened areas concentric to the radials, and sometimes alternating light and dark bands conforming to growth lines on the radials. Type 3 has sloping lines crossing the radials, concave chevrons on the deltoids, and darkened areas on the lower radials, concentric to the ambulacra and on the basals. Type 4 has dark dots concentric to the lower ambulacra, arched chevrons on the deltoids and transverse lines abutting the radials and on the basals. The color patterns are original and may have been exposed on the outside of the integument.

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