92 BRACHIOPODS. 



Athyris trinuclea (HALL). 



Terebratula trinuclea, Hall, 1858: Geology Iowa, vol. I, p. 659, pi. xxiii,, 



figs. 4a-c. 

 Spirigera reflexa Swallow, 1863: Trans. St. Louis Acad. Sci., vol. II, p. 



88. 



A very variable shell like A. argentea, the trilobate char- 

 acter being usually more pronounced than in most other forms 

 of the group. 



Horizon and localities. Lower Carboniferous, Saint Louis 

 limestone : Barrett station ( St. Louis county ). 



Athyris subquadrata HALL. 



Athyris subquadrata Hall, 1858: Geology Iowa, vol. I, p. 703, pi. xxvii, 



figs. 2a-d. 

 Spirigera clintonensis Swallow, 1863: Trans. St. Louis Acad. Sci., vol. II, 



p. 89.' 



A rather large, trilobate form, much like the smaller A. 

 trinuclea. 



Horizon and localities. Lower Carboniferous, Kaskaskia 

 limestone : Ste. Mary ( Ste. Genevieve county). 



Athyris sublamellosa HALL. 



Athyris sublamellosa Hall, 1858: Geology Iowa, vol. I, p. 702, pi. xxvii, 



figs. la-c. 

 Spirigera americana Swallow, 1863: Trans. St. Louis Acad. Sci , vol. II, 



p. 89. 



A large shell with prominently imbricated concentric lines 

 of growth. 



Horizon and localities. Lower Carboniferous, Kaskaskia 

 limestone : Ste. Mary (Ste. Genevieve county). 



Athyris argentea ( SHEPARD ). 



Plate xxxix, figs, lla-d. 



Terebratula argentea Shepard, 1838: Am. Jour. Sci., vol. XXX IV, p. 152. 

 Terebratula subtilita Hall, 1852: Stansbury's Exped. Gt. Salt Lake, p. 409, 



pi. iv, figs, la-b, and 2a-b. 

 Terebratula subtilita Schiel, 1855: Pacific R, R. Sur., vol. II, p. 108, pi. i, 



fig. 2. 

 Terebratula subtilita Hall, 1856 : Pacific R. R. Sur. , vol. Ill, p. 101, pi. iU 



fig. 4. 

 Terebratula subtilita Davidson, 1857: Monog. Brit. Carb. Brachiopods, p. 



18, pi. i, figs. 21, 22. 



