Protolenus (Protolenus) densigranulatus   Matthew 1892

This is characterized by a thoracic axis that is as wide or wider than the pleural axes (the left and right sides of the thorax).  A "half moon" pygidium and stout genal spines is also characteristic.  They are more commonly found without genal spines.  The glabella is wider at the base and larger than the Hamatolenus genus.  These are medium sized trilobites like Hamatolenus being about two to three inches long.  The first photo shows the test covered in what looks like fine granules, hence the name, densigranulatus. Also note the fine preservation of small axial spines/nodes on the thoracic axis.  

 

 
 
Kenjiro 2009.5.10 (Edited 2019.11.15)