I20 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 75 



probably flattened even before compression in the shaly matrix in 

 which they are preserved. 



Cephalon. — Cephalon relatively large, more than half as long as 

 the entire shield. Cranidium only preserved, broadly convex, rudely 

 semi-circular in outline, the relative proportions varying quite widely 

 with the degree and direction of compression. Glabella about three- 

 fourths as long as the cranidium, subrectangular in outline; dorsal 

 furrows rather broad but deeply impressed, converging very slightly 

 toward the front ; anterior furrow transverse not quite so deep as 

 the dorsal ; antero-lateral margins of glabella sharply rounded ; gla- 

 bellar furrows obscure and often obliterated, the posterior pair 

 inclined to the axis at an angle of about 45° and persisting almost, 

 but not quite, to the occipital groove, the medial and anterior pair 

 even more obscure than the posterior and more nearly at right angles 

 to the axis, all three pairs of furrows disappearing rather abruptly 

 so that the unsculptured medial portion of the glabella is of approxi- 

 mately the same width as the grooved lateral areas; a fourth pair of 

 glabellar furrows perceptible in some individuals between the anterior 

 extremity and the third pair counting from the occipital ring ; occipi- 

 tal groove deep and quite wide, persistent across the crest of the 

 glabella, the anterior margin of the groove more steeply cut than the 

 posterior ; occipital ring rather narrow, slightly expanded medially, 

 apparently not nodose. Fixed cheeks broad and flattened, the dis- 

 tance from the palpebral lobe to the dorsal furrow equal approxi- 

 mately to the width of the glabella; postero-lateral lobe short, and 

 sagittate in outline, the obtusely angulated extremity slightly inclined 

 posteriorly ; posterior groove deeply channeled and quite broad, its 

 inner termination in line with the posterior portion of the occipital 

 ring ; posterior margin conspicuously elevated opposite the palpebral 

 lobe, wedging out toward the axis. Palpebral lobe short, narrow, 

 somewhat arcuate, about one-third as long as the glabella exclusive 

 of the occipital groove and ring, placed rather far back opposite the 

 lobe between the posterior and medial glabellar furrows. Ocular 

 ridge narrow, cordate, arching obliquely across from the anterior 

 extremity of the lobe and intercepting the dorsal furrows as the 

 origin of the fourth pair of glabellar furrows. Frontal limb wide, 

 sharply elevated in front of the glabella, and then abruptly turned 

 down so as to form a semi-circular ridge that extends back beyond 

 the ocular ridges. The fine venation radiating from, in front of the 

 glabella passes over the ridge and down the nearly perpendicular 

 front slope to the narrow frontal border, which is a little thickened 



