CONTRIBUTIONS TO PALEONTOLOGY. 139 



width of the glabella. Dorsal furrow strongly defined at the 

 sides,- and distinctly limiting the glabella in front. 



Fixed cheeks comparatively narrow, spreading opposite the centre 

 of the palpebral lobe j the posterit)r limb about the same width 

 as the cheek anterior to the eye, and deeply grooved ; the fron- 

 tal limb broad and nearly flat, without elevated or thickened 

 border, or with this feature scarcely perceptible. The extension 

 of the frontal limb is equal to a little more or less than half 

 the width of the glabella. 



Movable cheeks large, somewhat triangular, with a deep sinus at 

 the inner angle for the place of the eye, convex towards the 

 eye, and flattened or concave between this convexity and the 

 outer margin : exterior limb scarcely thickened, produced 

 posteriorly into a thin flattened spiniform process. 



Hypostoma broad ; the body convex and subcircular or very 

 broadly oval, with margins expanded and furrowed near their 

 antero-lateral angles. 

 In small specimens, there is a minute node near each anterior 



angle. 



Thorax wide, the axis narrow, moderately convex, strongly de- 

 fined by the dorsal furrow, less than one-fourth the entire width 

 of the body : lateral lobes nearly flat, the segments marked 

 by a simple groove which begins on the upper margin of the 

 rib at the dorsal furrow, and, becoming central at a point about 

 half the length of the rib, continues in the same direction, 

 bending downwards and extending into the slightly recurved 

 extremity. 



Pygidium broad, more than once and a half as wide as long : axis 

 very prominent ; the lateral lobes convex near the axis, and, 

 sloping rather suddenly downwards, become depressed and 

 flattened towards the margin. Axis marked by four annulations, 

 exclusive of the lower terminal one and the anterior articula- 

 ting joint : lateral lobes marked by four ribs which are deeply 

 divided from their origin, with a slight elevation close to the 

 posterior extremity of the axis and the anterior simple rib. 

 The extremities of the ribs terminate in a broadly expanded 

 limb, which is gently curved at the sides, and produced at the 

 postero-lateral angles into a short process, leaving a wide gen- 

 tly curving posterior margin. 



The surface of the movable cheeks, of the caudal expansion, 

 and of the extremities of the thoracic segments, is strongly striate. 



