250 



TRILOBITA 



CHAP. 



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



B 



FIG. 151. A, Phillipsia gemmulifera. Phill., Carboniferous. B, Arethusina konincki, 

 Barr., Ordovician. C, Dalmanites limiilurus. Green, Silurian. (After Hall.) D, 

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

 Acidaspis dufrenoyi, Barr., Silurian. (A, B, from Zittel ; D, E, F, after Barrande ; 

 natural size.) 



convex or inflated, and distinctly denned. The facial suture 

 passes from the lateral to the front margin. The free cheeks 



