258 THE CHICAGO ACADEMY OF SCIENCES. 



as eight or more; lateral furrows nearly obsolete, represented 

 by depressions which are scarcely distinguishable from the de- 

 pressions between the rows of tubercles. Cheeks with a nar- 

 row, rounded, more or less indistinct marginal border which 

 bears about three or four tubercles anteriorly on each side of 

 the glabella, arranged in a row; produced posteriorly into genal 

 spines of moderate length; the surface elevated just outside the 

 dorsal furrow into sub-conical -bases for the support of the 

 long, slender, Spreading peduncles which support the eyes, 

 around the base of each eyestalk is a more or less irregular circle 

 of tubercles similar to those upon thje glabella with a few ad- 

 ditional irregularly scattered tubercles upon the inner slopes 

 of the cheeks toward the glabella, the remaining surface of the 

 cheeks and the eye-stalks smooth. 



Thorax with well defined axial furrows, the axis strongly 

 convex, its width a little less than that of the pleural lobes, 

 segments eleven in number, the next to the last one bearing a 

 long slender spine which rises from the median line of the axis 

 with a moderate backward curve. 



Pygidium sub-triangular in outline, produced posteriorly 

 into a long, slender, upwardly curving spine; axis strongly 

 defined, the elevated portion extending into the posterior spine, 

 it is divided into twenty or more short segments which in the 

 casts are not continuous across the median region, and bears 

 six tubercles along the median line, which lie between the 

 inner extremities of the pleural ribs except the most anterior 

 ones. Pleural lobes slightly flattened adjacent to the axial 

 furrows, and then curving abruptly downward to the lateral 

 margins, marked by seven pleural ribs which are stronger ante- 

 riorly, the last one or two often becoming nearly obsolete, each 

 rib bears a well-defined tubercle just outside the dorsal furrow, 

 and two or three of the median ribs often bear a second tubercle 

 a short distance outside these first ones. A pair of tubercles 

 is also present at the base of the caudal spine, with two or three 

 additional indistinct ones along the lateral margins in front of 

 the base of the posterior spine. 



The dimensions of a small, more or less imperfect, but 

 nearly complete specimen are : total length exclusive of the caudal 

 spine 29 mm., length of cephalon 8 mm., length of thorax 12 

 mm., length of pygidium, exclusive of spine 9 mm. The dimen- 

 sions of a nearly perfect cephalon are: length along median 

 line 10 mm., distance between tips of genal spines 30 mm., 

 greatest width of glabella 10.5 mm., width of axis at occipital 



