250 



TRILOBITA 



Fam. 12. Cheiruridae (Fig. 151, D, E).— The glabella is 



Fig. 151. — A, Phillipsia gemviulifera. Phill., Carboniferous. B, Arethusiiia konincki, 

 Barr., Ordovician. C, Dalvianites limulurus, Green, Silurian. (After Hall.) D, 

 Cheirurus insignis, Beyr. , Silurian. E, Deiphon forbesi, Barr., Silurian. F, 

 Acidaspis diifrenoyi, 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 



