BY R. ETHERIDGE, JUNR., AND JOHN MITCHELL. 505 



continuous, conspicuously deflected laterally; genal angles pro- 

 duced into strong spines reaching to the sixth segment of the 

 thorax; neck furrow distinct, particularly where it joins the axial 

 furrows, continuing across the lateral lobes subfalcately with 

 Increasing distinctness and width; facial sutures anteriorly rather 

 straight to the border, thence continuous, posterior portions from 

 the hinder ends of the eyes passing out laterally and falcately, 

 cutting the borders of the free cheeks in a line with the base of 

 the eye. Eyes large, each has 32 to 40 or even more vertical 

 rows of lenses with a normal number of eleven in each central 

 row, and in odd cases twelve to fourteen, giving an aggregate of 

 about 400 lenses in a single eye of some mature specimens; the 

 lentiferous face forms a subsemicardioid curve, alcove sloping back- 

 ward at an angle of about 40°, below bounded by a shallow groove, 

 height diminishing more gradually posteriorly than anteriorly; 

 lenses spherical, closely packed in the vertical rows, which are 

 separated by distinct spaces or partitions. 



Thorax. — About equal in length to the combined width 

 of one pleural lobe, and the axis or about two-thirds of 

 its total width, and greater than that of either the head or tail, 

 suboblong or subfusiform; axis subfusiform, greatest width 

 at fourth or fifth segment, where it is slightly greater 

 than the width of the neck ring; arched most prominently 

 posteriorly, rather flat anteriorly; segments thickened at their 

 bases, moderately arched; some axes show faint trilobation 

 caused by feeble depressions traversing their length, these depres- 

 sions are accentuated by rows of tubercles, one on each side, about 

 midway between the central line and the axial groove; pleurae 

 one and one-third times as wide as the thorax, and between the 

 axial grooves and fulcra rather horizontal, outer ends moderately 

 deflected and recurved, the latter feature becoming more pro- 

 nounced posteriorly; pleural grooves wide and shallow, beginning 

 at the angles of junction with the axial grooves and passing out 

 posteriorly at the bases of the claw-like ends, thus traversing the 

 pleurte diagonally, anterior ridges much stronger than the pos- 

 terior, and passing across to the posterior edges at about midway 



