Naraoia.

Naraoia (nuh-ROY-uh) was a soft-shelled trilobite-like animal with a posterior shield and an anterior shield. Walcott described Naraoia as a crustacean because of its large carapace. But now it is believed to be a trilobite-like animal because scientists know that it had soft parts under the carapace.

Even though Naraoia could swim for a very short period of time, its armor was too heavy to allow Naraoia to swim for very long. Naraoia probably crawled along the sea floor in search of prey. Some specimens of Naraoia show bite marks, so it was probably good prey for predators such as anomalocarids. Naraoia could be up to 4 cm long.

Click the image to see Naraoia crawl across the sea floor.

This fossil of N. compacta is one of the best preserved Burgess Shale fossils. It's a complete specimen and has well-preserved appendages. According to Stephen Jay Gould, it can be photographed unretouched, unlike most other Burgess Shale fossils.

References:

http://www.trilobites.info/naraoia.htm

http://evolution.berkeley.edu/evolibrary/article/_0/cambrian_17

http://paleobiology.si.edu/burgess/naraoia.html

http://burgess-shale.rom.on.ca/en/fossil-gallery/view-species.php?id=86&ref=i&

Wonderful Life, Stephen Jay Gould, pg. 87