34 Trans. Acad. Sci. of St. Louis. 



ever, they agree closely with this species, which was originally 

 described from the Waverly Sandstone at Granville, Ohio. 



Elymella missouriensis Miller and Gurley. 



PI. iii.f. 9. 



Shell about 23 ram. in length, subelliptical in outline, nar- 

 rower in front, the height one-half the length. Anterior end 

 narrowly rounded, posterior end narrowly rounded below and 

 arcuate above and forming an obtuse angle with the hinge- 

 line, basal margin arcuate. Hinge-line straight, about two- 

 thirds the extreme length of the shell, sloping to the anterior 

 end. Hinge-teeth unknown. Valves convex, gibbous in the 

 umbonal region ; beaks prominent, placed near the anterior 

 end and incurved over the hinge-line. Posterior cardinal 

 slope concave, the umbonal ridge subangular at first but grad- 

 ually merging into the general convexity of the shell. Surface 

 ornamented with regular concentric striae about 1 mm. apart 

 upon the posterior umbonal slope, but becoming much closer 

 towards the anterior end of the shell. 



Remarks. This species was originally described from the 

 Chouteau limestone near Sedalia, Missouri. The Northview 

 specimen is a little more elongate and has a more pointed 

 posterior extremity with an obtusely angular junction between 

 the posterior and dorsal margins, than the illustration of the 

 type specimen of the species. This difference, however, is 

 not considered sufficient to establish a distinct species. 



PrOMACRUS WEBSTERENSIS U. Sp. 



I'l.II.f.2. Pl.III.f.l. 



Shell large, rather compressed, 15 cm. or more in length, 

 the height a little more than one-fourth the length. Basal 

 margin nearly straight from end to end ; anterior margin 

 narrowly rounded at the extremity ; posterior margin sharply 

 rounded below, obliquel}' truncated above, meeting the dorsal 

 margin in a rounded, obtuse angle ; dorsal margin straight 

 posteriorly and subparallel with the basal margin, also nearly 

 straight anterior to the beak but sloping downward to the 

 narrowly rounded anterior end. Beaks broadly obtuse, sit- 

 uated a little anterior to the middle of the valves. A 



