14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. IO3 



The wide glabella is constricted to a rounded anterior outline. The 

 occipital and first pair of glabellar furrows are narrow, but clearly 

 defined, and in exfoliated specimens the anterior pair is visible. The 

 dorsal furrow is wide and deep. The glabella, slightly flattened on 

 top, stands wholly abcnc the fixigenes and the dorsal furrow on the 

 sides while in front it overhangs that furrow. Longitudinally the head 

 is highly convex, the glabella curving throughout has its greatest 

 convexity in the anterior half. The brim is narrow, its position con- 

 tinuing the downward trend of the cranidial curvature. At their 

 widest point the fixigenes are a little more than one-third the glabellar 

 width. They contract rearw^ard from their widest point which is 

 situated anterior to the middle of the head. Their anterior portion is 

 about half their average width, but because of high convexity in 

 dorsal view they appear much narrower. Laterally the fixigenes are 

 considerably curved and like the glabella have the greatest curvature 

 at the outer margins where they drop off to a wide palpebral furrow 

 and eye band, which is practically horizontal. Longitudinally the 

 fixigenes rise abruptly from the depressed posterolateral limbs, and 

 then slope gradually until near the forward end of the eye, where 

 they drop ofif abruptly to meet the depressed brim. 



Honey Creek limestone ; (loc. Sqw) west side of the West Timbered 

 Hills; and (loc. I2p) 4 miles east of Alpers, Arbuckle Mountains, 

 Oklahoma. 



Holotype. — U.S.N.M. No. 108645a; paratype, No. 108645b. 



IRVINGELLA ARBUCKLENSIS, new species 

 Plate 2, Figures 28-33 



This is a very prolific species of average size. The glabella, normal 

 in size and depth of furrows, is constricted toward the front. The 

 dorsal furrow is relatively shallow, but the glabella is well differen- 

 tiated in cross section because it stands completely above the fixigenes. 

 Laterally the glabella is evenly curved, attaining a height equal to 

 about one-half its width. In the opposite direction the considerable 

 convexity is attained by declivity of the forward moiety. The brim, 

 of normal width, slopes downward from the anterior furrow. The 

 fixigenes are slightly less than half the wndth of the glabella; thus 

 the eyes are set at a considerable angle to the dorsal furrow. They 

 increase in width from front to back. The anterior portion is flexed 

 downward into a nearly vertical position and so is much wider than 

 appears in dorsal view. The eyes extend from about the occipital 

 furrow forward only to the anterior glabellar furrow, and hence are 



