62 Field Museum or Natural History — Geology, Vol. IV. 



marginal furrow; cheeks subtriangular in outline, depressed conical in 

 form, sloping gradually to the palpebral lobes; eyes small, pedunculate, 

 holochroal ; facial sutures originating at the genal angles, passing directly 

 to the palpebral lobes, which they cross, thence obliquely forward, cross- 

 ing the dorsal furrows and subparallel to the furrow crossing the gla- 

 bella, until they meet the rostral plate, where they bend abruptly forward 

 to the anterior margin; free cheeks large, more than twice the size of the 

 fixed cheeks; marginal borders well-defined by the marginal furrows, 

 those of the posterior margin narrow, those of the lateral margins wide, 

 gradually narrowing to the anterior margin; genal angles rounded, ending 

 in a large tubercle. Surface of the glabella covered with large rounded 

 tubercles, that of the cheeks near the dorsal and lateral marginal fur- 

 rows tubercular, other portions covered with elongated pits radiating 

 from the eyes; surface of the occipital segment and marginal borders 

 finely granulose. Hypostoma broadly elliptical, convex. 



Thorax composed of eleven segments; axis convex, about the 

 same width as the pleurae; tapering slightly posteriorly, pleurae 

 curving regularly to the lateral margins; surface of the thoracic seg- 

 ments finely granulose, ornamented with indistinct nodes; these vary 

 from two to four on the axis and one or two on each pleura; no pleural 

 grooves. 



Pygidium triangular, convex, width somewhat 'greater than the 

 length, rounded posteriorly, no caudal spines. Axis convex, conical, 

 occupying about one-third the anterior margin of the pygidium, with 

 many annulations, which diminish in size and distinctness posteriorly so 

 that the number visible depends to a great extent on the amount of 

 abrasion to which the specimen has been subjected; most of the annula- 

 tions bear two to four rounded nodes, having decided pits in their 

 apices. Pleurae composed of seven distinct ribs, which curve slightly 

 upward and then downward and backward to the margins; each rib 

 ornamented with two or more rather indistinct nodes near the dorsal 

 furrows and with a prominent knoblike distal end. 



Dimensions of the type specimen: 



Length of cephalon 10 mm. 



Width of cephalon at genal angles 17.5 mm. 



Length of glabella exclusive of occipital segment 8.4 mm. 



Width of glabella on anterior margin 8.0 mm. 



Width of glabella on occipital furrow 5.0 mm. 



Entire length of body measured on a coiled specimen. ... 32.0 mm. 



Length of pygidium (Mus. No. P 16930) 8.2 mm. 



Width of pygidium 9.6 mm. 



Width of axis at anterior margin 3.6 mm. 



