Calymene cerebra

 
scale in cms

CLASS - Trilobite
ORDER - Phacopida
FAMILY - Calymenidae
GENUS/SPECIES - Calymene cerebra

ROCK UNIT - Niagara Group

AGE - Middle Silurian (425 million years old)

LOCALITY - Milwaukee, Wisconsin, USA

Although the outer shell of trilobites were hard and resistant to decay, they weren't indestructible. The Niagara Group limestones were chemically altered to a rock called dolostone when the rocks were buried below the Earth's surface. The deep groundwaters that caused this change also dissolved the hard shell of the trilobites. This left only impressions in the surrounding rock that we call molds.

PRI 42102