l8 SMITHSONIAN MlSCEt.LANEOU.S COLLECTIONS VOL. IO3 



glabellar furrows are about equally deep and nearly parallel, and a 

 faint second pair is present. Glabella stands completely above the 

 fixigenes and is moderately and evenly curved laterally. Longi- 

 tudinally there is considerable curvature which increases in amount 

 from the occipital furrow forward. Brim of moderate width and 

 development ; only slightly thickened. Anterior fixigenes a little wider 

 than brim. At their widest point they are about one-fourth the width 

 of the glabella, decreasing in. width toward the occipital furrow. 

 Moderately bowed eyes' extend forward nearly to the front end of 

 the glabella. 



Wilberns formation ; ( loc. 69) Honey Creek, 8 miles southeast of 

 Llano, Texas. 



Hololypc.—V.S.NM. No. 108653. 



IRVINGELLA ARDMORENSIS, new species 

 Plate 3, Figures 7-12 



Only one comparatively large species of Irvingclla occurs at this 

 locality. An unusually wide variation in size has been allowed, for 

 some cranidia are larger, while others are less than one-third the 

 size of the s]x;cimens illustrated. 



The glabella is nearly quadrangular in outline, tapering slightly 

 forward to a rounded frontal outline in which there is a slight 

 flattening medially, hi cross section the glabella has considerable 

 elevation produced by a fairly even ciu'vature. Longitudinally it is 

 also high, as shown by the illustrations. The glabellar profile shows a 

 rise from the rear margin in a shallow curve to the front lobe of the 

 glabella and then a very steep drop to the anterior furrow. Brim 

 narrow and slightly thickened. Anterior fixigenes taper rapidly to 

 the narrow brim, at their widest point being about one-third the 

 glabellar width. The fixigenes have only a slight convexity. The eyes 

 are a little more than half the length of the glabella and are only 

 moderately bowed. 



Lloney Creek limestone ; (loc. I2p) 4 miles east of Alpers, Arbuckle 

 Mountains, Oklahoma. 



Holoiy/^c. — U.S.N.M. No. 108654a; paratype, No. 108654b. 



IRVINGELLA PLENA, new species 

 Plate 3, Figures 13-15 



This species, represented by numerous cranidia, is found in asso- 

 ciation with several other forms from which it is distinguished by its 

 plumpness. 



