FOSSILS OF THE LOWER SILURIAN. 245 



slightly convex; annulations indistinctly marked. Pleura curving backward 

 near the outer ends and pointed at the extremity ; marked along the middle 

 by a broad, shallow furrow, which occupies one-half of the width for a dis- 

 tance of nearly two-thirds the length of the rib, becoming obsolete near 

 the free flattened extremity. 



Pygidium broadly elhptical, scarcely twice as wide as long, anterior 

 face much less convex than the posterior, which sometimes becomes irregu- 

 larly paraboloid in the slate from distortion. Axial lobe less than one-third 

 of the entire width, and rapidly tapering posteriorly ; about four-fifths as 

 long as the shield, and terminating just within the rather broad, recurved 

 marginal lining of the under surface in an obtusely-rounded point ; axis 

 marked by six strong, rounded rings, exclusive of the terminal one ; lateral 

 lobes depressed-convex, marked by three or four obscure ribs, which, when 

 compressed in the slates, become very faint and obscure. 



The material from which the above description is taken is in a very 

 unsatisfactory condition, being fragmentary and much distorted by the 

 slipping and contortions of the shale in which they are imbedded, so that 

 the features of form as here given may be somewhat modified on finding 

 other and more perfect material. The great length of the glabella will serve 

 as a distinguishing feature in the identification of the species. 



Formation and locality. — In greenish and reddish shales of the age of the 

 Quebec group, at East Canon, Oquirrh Mountains, Utah. Collected by J. 

 E. Clayton and S. F. Emmons. 



Ogygia parabola n. sp. 



Plate II, fig. 35. 



Pygidium long-paraboloid, posterior to the antero-lateral angles, with 

 a slight emargination at the posterior border ; front margin somewhat irreg- 

 ularly arcuate ; surface flattened, or very gently convex, and in the cast 

 showing a very wide marginal lining on the under surface, which extends 

 to nearly one-half the width of the lateral lobes on the anterior margin, and 

 very gently widening posteriorly. Axis convex, wide and bulbous in front, 

 narrowed and cylindrical below for about four-fifths of its length; the 

 anterior bulbous portion forming a single strong annulation, once and a 



