Olenellus thompsoni, a typical olenellid trilobite, approximately 1.3 inches (3.4 centimeters) long. These are the earliest group of common North American trilobites, occurring only in the early Cambrian.
Olenellus thompsoni, a typical olenellid trilobite, approximately 1.3 inches (3.4 centimeters) long. These are the earliest group of common North American trilobites, occurring only in the early Cambrian.