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NEW YORK STATE MUSEUM 



tions with very narrow furrows. The fourth and eighth annula- 

 tions bear two strong nodes on the axis and the 9th, 12th 

 and 13th show fainter traces of them. The broad and flat 

 pleurae bear 15-17 flat ribs grooved by narrow and sharply incised 



oblique furrows ; the ribs bend abruptly backward near the margin 

 and are discernible almost to the edge of the shield. They are also 

 sparsely but very irregularly nodose, the nodes being large and 

 coarse. The whole surface is finely granular. 

 Lower Devonic. Perce rock, P. O. 



