126 NEW YORK STATE MUSEUM 



though the third pair are very short and the median spine apparently 

 absent. Ceraurus scutiger shows three pairs of spines on 

 the pygidium, and a short median spine, thus making a close 

 approach to the required ancestor, but the great spines are still 

 much longer than the spines between, and the development of the 

 various spines is very unequal. 



Horizon and locality. The specimens are from the lower part 

 of the Upper Chazy at Little Monty bay, Chazy, N. Y., and the 

 quarry near the bay at Cooperville, N. Y. The large pygidium may 

 be designated as the holotype and the other figured specimens as 

 paratypes. All were collected by Dr Rudolf Ruedemann and are 

 in the New York State Museum. The hypostoma. previously 

 described was collected in the lower part of the Upper Chazy at 

 Cooperville, N. Y. 



