G2 A CoNTiiinuTioN to the Lower Devonian Rvunas of Maryland 



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 aliruptly 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 

 ril) 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. 



" Surface granulose, the granules being somewhat stronger on the more 

 prominent parts of the head and in front of the eyes, while on the thorax 

 and pygidium there is usually a stronger row of granules along the lower 

 margins of the articulations. The granulose marking, however, is subject 

 to considerable variation, either from accidental or other causes ; and some 

 specimens of the pygidium present a line granulose texture, visible only 

 under a lens." Hall, 1859. 



Occurrence. — Helderberg Formation, Coeymans Member. Devil's 

 Backbone, Dawson. Xew >Scotlaxd Member. Devil's Backbone, Cor- 

 riganville, Dawson, Tonoloway ? 



Collections. — Maryland (Jeological Survey, U. S. National ]\Iuseum. 



