TREXTOX CONGLOMERATE OF RYSEDORPH HILL 49 



appear faint projections. It is suppo>sed that they represent 

 muscle scars. 



Fostrum yerj long, prismatic. Tvith a subrliombic section, 

 upper sides grooved; strongly bent upward. Fixed cheeks 

 having the shape of slightly recurving cusps, moderately convex, 

 sloping rather abruptly downward at the frontal margin and 

 gently upward in front of the neck segment, lying ventrally with 

 their frontal part below the middle of the glabella, where a 

 narrow, flat, vertical rim is developed. A line which appears 

 most distinctly in casts as a narrow ridge, passes from the 

 posterolateral afigle of the fixed cheek obliquely forward across 

 the same in the direction of the anterior glabellar pits. This 

 line, in its direction and extent, seems to be an exact homologue 

 of the eye line of Tretaspis and other trilobites and prob- 

 ably indicates the former presence and situation of the eyes 

 in this genus, of which only blind forms are known. Suture 

 line beginning directly below the second pair of glabellar pits, 

 at the end of the flat marginal rim, running first a short dis- 

 tance outward, then turning rather abruptly backward to a point 

 Tiear the neck furrow, where it again curves outward, intersecting 

 the occipital ring in oblique direction. Free cheeks were not 

 observed, but, from the direction of the suture line, it is sup- 

 posed that they were rather small, subtriangular plates. Dorsal 

 furrows strongly marked. Neck furrow slightly curved, faint, 

 deeper toward the genal angles. Surface of cranidium entirely 

 smooth. 



Thorax not observed. 



PygMium broadly triangular; axis well defined, broad, occupy- 

 ing about one third of the width of the plate, tapering slightly 

 ^nd ending bluntly near the terminal point; depressed convex, 

 highest in the middle. Rarely more than six annulations, indi- 

 cated by faint transverse furrows. Pleurae level, smooth, without 

 indications of pleural ribs, with a deep furrow running parallel 

 to the anterior margin, nearly vertically beveled along the mar- 

 gins, the upper edge of the bevel with an acute linear rim, sides 

 :finely striated parallel to the margin. 



