GIRTY, THE WEWOKA FORMATION OF OKLAHOMA 155 



comes so changed that its surface is essentially vertical, and so that the an- 

 terior outline of the glabella is terminal, when the head is seen from above. 

 Outline of the facial suture very sinuous. The sutures almost come together 

 at the end of the glabella, diverging strongly as their course is traced back- 

 ward. At the sulcus which defines the border, they assume an opposite direc- 

 tion, contracting gently for an equal distance. They make a strong arch 

 around the palpebral lobes and from the neck furrow pass somewhat obliquely 

 outward to the articulating margin. Glabella much wider toward the front 

 than behind, occupying nearly the whole of the cranidium, so that there is little 

 of the fixed cheek, except the rather small palpebral lobes. The neck furrow 

 is strong and broad, passing almost directly across the cephalon to the two 

 sulci defining the border. The neck ring is very broad, oblique, prominent, 

 much wider than the sort of band with which it is continuous, which is pro- 

 duced on either side by the neck furrow. The posterior part of the glabella 

 is subdivided into three knob-like lobes by two oblique furrows cutting off 

 the corners, so to speak, and a cross furrow connecting these parallel to, and 

 a little in front of, the neck furrow. These lobes are rounded, and the fur- 

 rows between coalesce around them into an undefined depressed area. A par- 

 tial and indistinct transverse furrow, a little in front, indicates a second 

 annulation of the glabella. The glabella is tumid, the palpebral lobes and 

 neck ring very prominent. The large, elliptical, many-faceted eye is strongly 

 oblique and the free cheek just external to the eye also slopes strongly down- 

 ward toward the border. A small subangular ridge passes around the outer 

 margin of the eye. 



The somatic segments are 9 in number, with a highly arched axial lobe 

 which comprises about one third of the entire width. The pleural lobes are 

 much depressed and defined from the axial portion by sharp sulci. They are 

 nearly planate over the median portion, but bend strongly and abruptly down- 

 ward about half way to the extremity. The pleural portion of each segment 

 is subdivided by a furrow which reaches almost to the axis. 



The pygidium is semi-elliptical in outline, broadly rounded posteriorly and 

 with a broad, smooth, oblique and depressed border which narrows somewhat 

 anteriorly. The axis is strongly and sharply elevated and defined by well- 

 marked grooves. It is flattened on top and nearly quadrate in section. The 

 lateral lobes are moderately inflated, the convexity being irregular, so as to 

 produce an angulation down the center of each, appearing on the segments 

 on either side as a row of prominences or nodes. The segmentation of the 

 pygidium is strong, produced by deep, sharp grooves which do not extend onto 

 the border nor onto the sides of the pygidium. They produce about 12 axial 

 rings and about 7 lateral ones. 



The surface is marked by granules or small nodes which appear on the 

 more prominent parts of the surface, on the basal portion of the glabella, on 

 the crest of the neck ring, along the little ridge under the eyes, and in rows 

 across the segments of the axis of both thorax and pygidium. The pleural 

 segments are either without these nodes or have them fewer, smaller and less 

 conspicuous. 



