Contributions to Palaeontology. 



133 



In the Trempaleau specimens the glabella is ovoid and 

 very gibbous ; the width and length to the occipital furrow 

 about as three to four, varying slightly in different speci- 

 mens, some of which are proportionally longer. The lateral 

 furrows reach about one-third across the glabella. The 

 anterior furrow is short and slightly oblique : the middle 

 furrow is more deeply impressed, and the posterior furrow 

 is more oblique and deeper, separating the posterior lobe 

 so that sometimes it appears like an ovoid tubercle. The 

 occipital furrow is either direct or a little arched forward, 

 sharply impressed: the occipital ring is short, triangular, 

 and extended posteriorly into a slender sharp spine, which, 

 including the segment, is about as long as the glabella. 

 The dorsal furrow is strongly defined, limiting the glabella 

 as distinctly in front as at the sides. The fixed cheeks 

 are narrow, convex or rounded longitudinally, a little wider 

 anteriorly, rarely showing ocular ridges: the posterior 

 limb is much extended. The frontal limb is convex, nar- 

 rower than the cheeks, marked by a sharp groove, and 

 terminated by an equally sharp, straight, narrow border. 

 The movable cheek is small, broadly triangular, with a 

 well-defined border which is prolonged into a short spine, 

 and on its inner angle supports a prominent occuliform 

 tubercle. 



The caudal shields associated with this species are 

 small, somewhat semicircular or paraboloid, with the 

 axis prominent and marked by about six rings. The lateral 

 lobes show four distinct ribs, which terminate in a narrow 

 border. 



"Well-formed specimens measure, from the neck-furrow 

 to the anterior limb, about 0-12 of an inch ; the glabella 

 being 0-10 of an inch in length, and about 0-07 of an inch 

 in width. 



The figures 1, 2, 3, 4, are views of the glabella and fixed cheeks, 

 a profile of the same, a separated movable cheek, and a pygidium, 

 which are all four times enlarged. 



