106 FIFTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



separated posterior lobe. The eyes are very prominent ( when 

 well preserved ) : the facial suture, as far as can be ascertained, 

 extends in an almost straight line from the eye to the frontal 

 margin. 



The hypostoma is ovate and very convex. Tlie thorax forms a pa- 

 rallelogram, the width being nearly twice the length, and but 

 slightly diminishing posteriorly : the axis strong, elevated, nearly 

 semlcylindrical; the dorsal furrow strongly marked, and the la- 

 teral lobes flattened or a little concave on their inner side, and 

 bending abruptly towards the margins. The furrow in the ribs is 

 almost linear, and the anterior limb is scarcely curved on its 

 margin. 



The pygidium is about equal in length to the head, semielliptical; 

 the axis prominent, elongate -conical, marked by thirteen or 

 fourteen rings, which are thickened at the base and rise vertical- 

 ly, bending a little backwards on the upper part of the sides, 

 making a curve which extends over the summit : the rings are 

 somewhat thickened at the summit, and may have been nodose 

 or spinose. Lateral lobes depressed towards the dorsal suture, 

 flattened or moderately convex in the middle and sinking abrupt- 

 ly at the sides, marked by about eleven ribs which are scarcely 

 (or not at all) grooved. The border is broadly concave, the outer 

 edge a little recurved. 



Surface of the head marked by small pustule-like papillae, which 

 are inclined backwards; the thorax and pygidium marked by 

 sharp pustulose points, which are sometimes arranged in rows 

 upon the articulations. The crest of the axis appears to have been 

 nodulose or spinose; but of numerous specimens examined, none 

 are quite perfect in these parts. 



A separated cheek shoves the eye to have been extremely elevated. 



This species has a well-marked expression, differing from all the others 

 described. The large glabella and distinct separation of the elongate poste- 

 rior lobe are very characteristic. The specimens examined consist of three 

 nearly entire individuals, and about eleven of the pygidia. 



Geological formation and locality. In the shales of the Hamilton group: 

 G-eneseo, Moscow, Pavilion, and Canandaigua and Skeneateles lakes, N.Y. 



[ September, 



