84 BRACHIOPODS. 



Shell of medium size, rather ventricose, semicircular to 

 subtrigonal in outline ; hinge-line equaling or longer than great- 

 est breadth of the valves. Ventral valve the more arched ; 

 beak incurved, prominent ; cardinal area well defined, moder- 

 ately high, somewhat curved ; foramen equilaterally triangular ; 

 median sinus well marked. Dorsal valve with an inconspicu- 

 ous beak ; mesial fold sharply rounded. Surface marked by 

 prominent radiating ribs, which usually group themselves into 

 fascicles of three to five or more. Lines of growth seldom well 

 defined. 



Horizon and localities. Upper Carboniferous, Coal Meas- 

 ures : Clinton ( Henry county ), Kansas City, Lexington. 



Spirifera rockymontana MARCOU. 



Spirifer rocky monian us Marcou, 1858: Geol. North America, p. 50. 

 Spirifer opimus Hall, 1858: Geology Iowa, vol. I, p. 711, pi. xxviii, figs. 



la-b. 



Spririfer subventricosus McChesney, 1860: Desc. New False. Foss., p. 44. 

 Spirifer boonensis Swallow, 1860: Trans. St. Louis Acad. Sci., vol. I, p. 



648. 

 Spirifera rockymontana Keyes, 1888 : Froc. Acad. Nat. Sci., Phila., p. 231. 



Closely related to S. keokuJc and probably the genetic suc- 

 cessor of that species. 



Horizon and localities. Upper Carboniferous, Upper Coal 

 Measures : Kansas City. 



Spirifera perplexa MCCHESNEY. 

 Spirifer lineatus (American authors, not Martin, 1809). 

 Spirifer perplexus McChesney, 1860: Desc. New False. Foss,, p. 43. 

 Spirifer lineatus Swallow, 1866: Trans. St. Louis Acad. Sci., vol. II, p. 



409. 

 Spirifer lineatus, var. stnato- lineatus Swallow, 1866 : Trans. St. Louis Acad. 



Sci., vol. H, p. 408. 



Shell much like an Ath^ris in general appearances, but 

 with distinct cardinal area. Surface nearly smooth, but hav- 

 ing faint radiating lines, and crenulated lines of growth, from 

 which spring minute spines, apparently. 



Horizon and localities- Upper Carboniferous, Upper Coal 

 Measures : Kansas City. 



