l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 53 



transverse except at the axial lobe, where it arches slightly forward ; 

 the slope from the central portion of the cephalon to the margin is 

 unbroken by any furrow and there is no clearly defined or raised rim. 

 Cranidium with a broad campanulate frontal limb that extends from 

 the anterior base of the eyes obliquely outward and forward and 

 directly forward from the glabella to the outer margin of the cepha- 

 lon ; the posterior limbs, on their inner side, occupy the space between 

 the posterior base of the eye and the posterior margin of the 

 cephalon and extend outward to the lateral margin with a gradually 

 increasing width ; there is no fixed cheek between the palpebral lobe 

 and the glabella; palpebral lobe about one-third the length of the 

 cephalon and situated a little back of the center ; it is slightly elevated 

 along the outer margin and slopes toward the dorsal furrow next 

 to the glabella. Glabella about three-fifths the length of the cepha- 

 lon; it has subparallel sides up to the front of the eyes, where the 

 sides curve inward and unite to form an obtusely rounded outline; 

 in front the glabella merges into the frontal limb, so as to make it 

 difficult to indicate a line of division between them; the glabella is 

 gently convex and more or less clearly marked by a narrow median 

 ridge, and, on each side of the ridge, two pits that indicate transverse 

 furrows, very much as do the pits on the glabella of Oryctoccplialiis^; 

 there is no trace of an occipital furrow or segment. Free cheeks 

 subquadrangular in outline; on their inner margin they support the 

 visual surface of the eye and from there slope gently to the outer 

 margin. The facial sutures cut the lateral margin of the cephalon 

 some distance in front of the genal angle and extend wth a little 

 backward curvature to the posterior base of the eye; after curving 

 over the eye lobe they extend obliquely forward at an angle of about 

 50° to the margin. 



Thorax with fourteen segments ; the first is nearly transverse, but 

 each succeeding pleural lobe bends back a little more than the one 

 preceding it, so that the pleural lobe of the posterior segment is bent 

 back parallel to the side of the pygidium ; the central axis of the 

 thorax is gently convex, with a low median ridge that rises into a 

 minute node on the two anterior segments ; it gradually widens from 

 the first to the seventh segment, and then narrows a little at each 

 segment back to the pygidium ; the pleural lobes are flattened between 

 the axial lobe and the angle where the pleurse bend more or less 

 backward ; each pleura has a broad, shallow, direct furrow that 

 extends from the inner end out to the backward curving portion of 

 the pleur?e ; the edge of the furrow and of the segment is marked by 



MValcott, 1886, Bull. U. S. Geol. Survey, No. 30. p. 210. 



