BRACHIOPODA. 147 



tions on each side are involved in the sides of the depression; at the same time the 

 mesial fold is very prominent, rounded and sloping almost imperceptibly into the general 

 contour of the convexity of the valve." 



Remarks — Only one specimen from southeastern Missouri has come to the writers' 

 attention. It is from the Hamilton of Little Saline Creek, Ste. Genevieve County, 

 probably Beauvais sandstone. The same specimen is preserved as internal and external 

 moulds. 



Spirifer grieri Hall 



Plate 33, figures 6, 7 and 8 



1857. Spirifer grieri Hall, Tenth Rep. N. Y. State Cab. Nat. Hist., p. 127. 



1867. Spirifera grieri Hall, Pal. New York, IV, pp. 194-195, pi. 27, fig. 29; pi. 28, 



figs. 17-23. 

 1897. Spirifer grieri Schuchert, Bull. U. S. Geol. Surv., 87, p. 392. 

 1901. Spirifer grieri Kindle, Indiana Dept. Geol. Nat. Res., 25th Ann. Rept., pp. 



638-639, pi. 8, fig. 6. 

 1909. Spirifer grieri Grabau and Shimer, North American Index Fossils, I, pp. 324- 

 325, fig. 412, a-c. 



Hall's description — "Shell gibbous, transversely oval or subquadrilateral, sometimes 

 longitudinally ovate, the proportions of length and breadth being very variable; hinge 

 line usually shorter than the width of the shell, with the cardinal extremities rounded; 

 valves subequally convex. 



Ventral valve gibbous or ventricose, most convex above the middle and nearly 

 opposite the center of the hinge line, and sloping very abruptly to the lateral margins; 

 sometimes regularly arcuate in the entire length and often arched in the upper part and 

 nearly straight below. Umbo prominent and much elevated above the hinge line; 

 beak more or less extremely incurved over the high arcuate area, which has a length of 

 from one-half to nearly two-thirds the width of the shell; mesial sinus wide and deep, 

 subangular in the lower part. 



Dorsal valve regularly arcuate, the greatest convexity near the middle and regu- 

 larly curving to the lateral margins; mesial fold prominent, sometimes rounded, but usu- 

 ally more or less distinctly angular; beak small, slightly incurved over a nearly vertical 

 narrow area. 



Surface marked by six, eight or ten more or less rounded simple plications on each 

 side of the mesial fold and sinus; while there are three or four distinctly bifurcating or 

 dichotomous plications upon the fold or sinus, giving six or seven at the margin of the 

 shell. In perfect specimens, the surface is covered by fine concentric lamellose striae, 

 which are crossed by delicate radiating striae." 



Remarks — This species is rare in southeastern Missouri. Five specimens are in 

 Walker Museum. Some of the specimens have well-developed plications in the sinus 

 but they extend only about half the length of the sinus. They are much smaller than 

 the plications outside the sinus and they bifurcate near the middle of the length. 



Occurrence — Grand Tower limestone of Little Saline Creek, Ste. Genevieve County. 



Spirifer pennatus (Atwater) 



Plate 33, figure 9 



1820. Terebratula pennata Atwater, American Jour. Sci. Arts, II, p. 244, pi. 1, figs. 2, 3. 



1841. Delthyris mucronata Conrad, Fifth Ann. Rep. Geol. Survey, New York, p. 54. 



1856. Spirifer mucronata Billings, Canadian Nat. Geol., I, p. 474, pi. 7, figs. 9, 10. 



1867. Spirifer mucronata Hall, Pal. New York, IV, pp. 216-218, pi. 34, figs. 1-23. 



1897. Spirifer pennatus Schuchert, Bull. U. S. Geol. Surv., 87, p. 401. 



1901. Spirifer pennatus Kindle, Indiana Dept. Geol. Nat. Res., 25th Ann. Rep., pp. 

 649-650, pi. 8, figs. 1, 2, 2a. 



