COLOR PATTERNS IN MISSISSIPPIAN (CHESTERIAN) BLASTOIDS

Ninety-one specimens of Pentremites Say from the Mississippian Chester ian display color patterns. The darker color patterns represent a thin veneer of pigmented calcite which is barely visible on a polished sur face or thin section, but which can be removed with dilute hydrochlori c acid. Preservation appears to be best in specimens from shallow mari ne clays and shales. The patterns represent four color patterns, each consisting of different shades of calcite, and ranging in color from t an to black. Color patterns generally, but not always. cross growth li nes. Type 1 has arched chevron patterns on the deltoids, horizontal li nes on the radials, and triangular bands on the basals. Type 2 has dar kened deltoids or concave chevrons on the deltoids and darkened areas concentric to the radials, and sometimes alternating light and dark ba nds conforming to growth lines on the radials. Type 3 has sloping line s crossing the radials, concave chevrons on the deltoids, and darkened areas on the lower radials, concentric to the ambulacra and on the ba sals. Type 4 has dark dots concentric to the lower ambulaera, arched c hevrons on the deltoids and transverse lines abutting the radials and on the basals. The color patterns are original and may have been expos ed on the outside of the integument.