88 ARTICULATA. 



No. 166. [447, Cast]. SphaerexochuS mirus, Beyrich. 



This curious Trilobite has a globular head, projecting eyes, 

 and ten pointed body-rings. It is from the Upper Silurian, 

 Beraun, Bohemia. 



No. 167. Triarthrus Becki, Green. 



A fine specimen of this typical Trilobite. From Utica Slate, near Utica, 

 N. Y. 



No. 168. Trinucleus ornatus, Burm. 



In this genus the pygidium is enlarged at the expense of 

 the thorax; the former is triangular; and the latter has 

 only six rings. The animal is never found fully rolled up. 

 From Lower Silurian, Lodenitz, Bohemia. 



No. 169. Trinucleus concentricus, Eaton. 

 Heads. From the Hudson River Group, Rome, N. Y. 



No. 170. [1296, Cast]. Climactichnites "Wilsoni, Logan. 



These tracks are now generally regarded as having been made by Trilobites. 



From the Potsdam Sandstone, Beauharnois, Canada. 



Size, 22 in. x 18 in. 



