6l8 TRANS. ST. I.OUIS ACAD. SCIENCE. 



prominent and located about the centre of the head, near the gla- 

 bella. The surface of the cheek is marked with a row of six 

 tubercles, located about midway on them and running parallel 

 to the border. 



Pygidium parabolic in form. Axis prominent, tapering gra- 

 dually to the lear into a blunt termination, not extended to the 

 border, marked with eleven rings, and with five rows of nodes, 

 a central and two lateral rows. The sides are marked with six 

 ribs, separated from each other by broad grooves. The ribs 

 are elevated ridges marked with a central row of nodes, varying 

 from four to two, according to their length. The limb is indi- 

 cated by a depression, the ribs extending on the limb and termi- 

 nating with a node. The two posterior ribs are prolonged into 

 spines, which extend over the border. 



Affinities. — This species approaches Brachytnetopus Lodi- 

 cnsis. Meek, from the Waverly group of Ohio ; it can be readily 

 distinguished from it, and from all other species of this genus, by 

 its characteristic pygidium. 



Geological position and locality. — Waverly Group, Sedalia, 

 Missouri ; from the cabinet of F. A. Sampson, Sedalia, Mo. 



