582 PALEONTOLOGY OF ILLINOIS. 



SCHIZODUS CURTUS, M. and W. 



PI. 26, Fig. 16. 

 Sclrizodus curtits, MEEK and WORTHEX, 1866. Proceed. Chicago Acad. Sci., Vol. I, p. 18. 



SHELL small, sub-orbicular, rather compressed, thin; 

 anterior side obliquely truncated, with a convex outline 

 above, and rounded into the base below; base deeply 

 rounded anteriorly, and ascending with a slightly straight- 

 ened outline, or even sometimes very faintly sinuous be- 

 hind; posterior side narrower than the front, nearly ver- 

 tically truncated, so as to form almost a right angle with 

 the base at the termination of the umbonal ridge, and more 

 or less rounded into the cardinal margin above; posterior 

 dorsal region behind the umbonal ridge compressed and 

 cuneate; cardinal margin sloping more or less behind the 

 beaks; beaks elevated, incurved, and placed very slightly 

 in advance of the middle; umbonal slope rather distinctly 

 angular from the beaks to the posterior basal extremity ; 

 ilanks just in advance of this ridge sometimes faintly con- 

 cave; surface marked with very fine concentric stria's. 



Length of the largest specimen from which the above 

 description was drawn up, 0.43 inch; hight, 0.33 inch; con- 

 vexity, about 0.16 inch. 



Locality and position Wabash cnt-oif near New Harmony, Indiana, 

 and in the nodules of argillaceous limestone over Coal No. 4, in Fulton 

 county, Illinois. 



Genus MYALINA, de Koninck. 

 MYALLNA PERATTENUATA, M. and H. 



PI. 26, Fig. 11. 

 Myalina perattenuata. MEEK and HAYDEN, 1858. Tran.s. Albany Institute. 



Position and locality This shell is abundant in a blue shale below 

 Coal No. 7, in the shafts at Springfield, Illinois. 



