250 TRILOBITA CHAP. 
Cheiruridae (Fig. 151, D, E).—The glabella is 
Ir 
—. 
af 
\\ 
E F 
Fig. 151.—A, Phillipsia gemmulifera. Phill., Carboniferous. B, Avrethusina koninchi, 
Barr., Ordovician. C, Dalmanites limulurus, Green, Silurian. (After Hall.) D, 
Cheirurus insignis, Beyr., Silurian. E, Deiphon forbesi, Barr., Silurian.  F, 
Acidaspis dufrenoyt, Barr., Silurian. (A, B, from Zittel ; D, E, F, after Barrande ; 
natural size.) 
convex or inflated, and distinctly defined. The facial suture 
passes from the lateral to the front margin. The free cheeks 
