252 TRILOBITA chap, viii 



Fam. 16. Lichadidae. — The body is broad, with a granular 

 dorsal surface. The qephalic shield is small and short, with 

 spinose genal angles. The glabella is broad, and its anterior 

 furrows are directed backwards, limiting a convex median lobe 

 and some lateral lobes. The facial suture extends from the 

 posterior to the anterior margin. There are nine or ten thoracic 

 segments with grooved pleurae, which have pointed ends. The 

 pygidium is large and triangular, with a short axis and a toothed 

 margin. Ordovician to Devonian. Genus : Lichas (sub-genera, 

 Arges, Bicranogmus, Conolichas, Ce7'atolichas). 



