Maryland Geological Survey 511 



transverse furrows strongly marked, the anterior one more deeply than 

 the others, and passing imperceptibly into the depression which circum- 

 scribes the frontal lobe : anterior lobe expanding, and becoming prominent 

 towards the inner angle of the eye ; the central lobe a little wider than the 

 posterior one. Occipital furrow narrow, shallow in the middle; its con- 

 tinuation in the posterior furrow of the cheeks being very strongly defined, 

 and becoming wider towards the exterior margin. 



"Eyes large, prominent, having an elevation of ten ranges of lenses, 

 while laterally there are thirty-seven ranges : the entire number of lenses, 

 in a specimen of medium size is 311. Between the lenses there is a small 

 round granule marking each of the angles of a hexagon, which circum- 

 scribes the lens. The entire rim of the eye is much elevated above the cen- 

 tral portion or palpebral lobe, and a deeper groove in the outer limb. 

 Hypostoma subhastate, with scarcely perceptible inequalities on the 

 margin. 



" Thorax with the axis somewhat abruptly convex, and about three- 

 fourths as wide as one of the lateral lobes, the articulations on each side 

 terminated by a broad node. The articulations of the lateral lobes of the 

 thorax marked by a deep longitudinal furrow, which leaves the elevated 

 portion above and below nearly equal, and the extremities bending rather 

 abruptly downwards. 



" Pygidium triangular, transversely convex ; the posterior extremity 

 acute, attenuate; the axis a little depressed towards the lower extremity, 

 which rises in strong relief above the border below. The axis is gradually 

 attenuate, the width at the posterior extremity being about one-third as 

 great as at the anterior extremity, which is about five-eighths as wide as 

 the greatest width of the lateral lobe at its upper margin : its outline is 

 curved and sometimes scarcely carinate, the latter feature more often seen 

 in the casts. The number of articulations in the axis is seventeen ; and in 

 each of the lateral lobes are eleven to thirteen ribs which are little wider 

 than the furrows which separate them; the whole bending downwards 

 towards the outer extremities, and uniting in a thickened border. Each 

 rib of the lateral lobe is marked by a longitudinal groove parallel with the 

 margins, and a little nearer to the upper than the lower margin. 



