250 



TRILOBITA 



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



FIQ. 351. A, Phillipsia gemmulifera. Phill., Carboniferous. B, Arethusina konincki, 

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

 C/ieirurus insignis, Beyr. , Silurian. E, Deiphon forbesi, Barr., Silurian. F, 

 Acidaspis dufrenoyi, Barr., Silurian. (A, B, from Zittel ; D, , 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 



