PLATE XVI— Continued. 

 Fie. 21. Posterior view of the same, showing' the projection of the genal spines beyond the thorax. 



Hamilton group. Canandaigua. Ontario county. 

 Fit;-. 22. A block of shale, shoving- a group of trilobites, including DalinanUes (C'ryplmiis) BootM, var. 

 Calliteles, Phacops rana and Oyphaspis craspedota. In Hie upper left-hand individual, the 

 right genal spine has been broken and healed before fossilization A little to the right of the 

 center of the block is shown the hypostoma of Dalmanites (Orypliwus) Boothi, var. Calliteles. 

 Hamilton group. Canandaigua, Ontario enmity. 



