360 F. JR. Cowper Heed — A Neiv JSf. American Trilobite. 



from tlie first, and is stronger and deeper than the others, but 

 similarly does not reach the axal furrows, terminating on each side 

 in an elongated pit within them, and thus marking off incompletely 

 the strong rounded occipital ring. Axal furrows straight and 

 strongly defined. 



Fixed cheeks nearly as broad as glabella behind ocular ridge, but 

 narrower in front of it. No frontal limb present, as glabella reaches 

 margin. Margin narrow, raised, and rounded, with concentric 

 striations on lower surface. Palpebral lobe arched outwards, 

 narrow, long, with a groove separating it from fixed cheeks. Ocular 

 ridge narrow, continuous with palpebral lobe and touching glabella 

 just in front of anterior transverse furrow. 



Free cheeks narrow, slightly longer than fixed cheeks and 

 reaching further back, furnished with narrow raised margin, produced 

 at genal angles into long straight spines obliquely directed outwards 

 and backwards and nearly as long as the thorax. 



Neck - furrow at base of cheeks strong, makes a sudden short 

 backward bend where it crosses from the fixed on to the free cheek ; 

 neck-ring narrow. 



Thorax composed of seven segments ; narrower than the head- 

 shield, being only the width of the ' middle-shield.' Axis cylindrical, 

 expanding slightly in width towards the middle, then gradually 

 tapering to the pygidium ; narrower than pleurae on each side. Axal 

 furrows deep. Axial rings rather wide, each possessing median, 

 slender, short spine (crushed down on body-ring or broken off) ; the 

 spine on the last one is longer than the others. 



Pleurte wider than axis, flattened and horizontally extended and 

 in close contact for three-fourths of their length, beyond which point 

 they become free, are slightly bent downwards and backwards, 

 contracting rapidly into slender, rounded, sharp spines. Each pleura 

 is marked with a strong diagonal fuiTow curving backwards from 

 the inner anterior angle on the axal furrow to the base of the spine. 



Pygidium large, nearly as long as thorax, wider than long, with 

 straight anterior edge ; composed of six segments. Axis long, 

 narrow, conical, obtusely pointed, consisting of five complete rings 

 and a small terminal segment, marked off by regular transverse 

 furrows. The axis does not reach the posterior margin, being only 

 about two-thirds the length of the pygidium. Lateral lobes com- 

 posed of six fused pleuras. The first three are of equal size and 

 preserve nearly the same width for their whole length, but end in 

 finely pointed slender spines projecting freely beyond the margin 

 and directed obliquely backwards, similar to those of the thoracic 

 pleuras. Each pleura is also marked by a strong diagonal furrow, 

 but the interpleural furrows are almost obsolete, so that the pleuras 

 appear fused together. The fourth pair of pleurte are of the same 

 width at their base as the preceding ones, but expand towards the 

 pygidial margin, beyond which they taper into long free stout spines 

 directed backwards and slightly outwards, parallel to the spines of 

 the first three pleurae but at least three times their length, giving 

 a distinctive and striking appearance to the pygidium. A strong 



