PLATE XVI—Continued. 
21. Posterior view of the same, showing the jirojection of the genal spines beyond the thorax. 
Hamilton gi-oup. CanmidMigua^ Ontario county. 
22. A l)lock of shale, showing a grouji of trilobites, including Dahnanites (Cryphwus) BootM, vai-. 
Calllteles, Phacops rana and OypJiaspis o'aspedota. In the 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 Dahnanites (Ci-yphcBiis) BootM, var. Calliteles. 
Hamilton group. Canandaigua, Ontario county. 
