502 GEOLOGY OF THE YELLOWSTONE NATIONAL PAEK. 



BRACHIOPODA. 



ATRYPA Dalman, 1827. 

 Atkypa reticularis Linne 1 . 



PL LXVI, figs, la, lb, lv. 



Atrypa reticularis Linne, 1767 : Systema Natime, ed. xii, Vol. I, p. 1132. Hall, 1852 : Pal. 

 New York, Vol. II, p. 72, PI. XXIII, figs. 8, Sa-Sn; p. 270, PI. LV, figs. 5a-5u. 

 Billings, 1863: Logan, Geol. Surv. Canada, Rept. Progress 1843-1863, p. 318, 

 figs. 335o-335c; p. 381, figs. 416a-416c. Hall, 1867 : Pal. New l r ork, Vol. IV, p. 

 316, PI. LII, figs. 1-3, 7-12; PI. LIII, figs. 3^19; PI. LIIlA, figs. 22, 23. Meek 

 and Worthen, 1868: Geol. Surv. Illinois, Vol. Ill, p. 132, PI. XIII, fig. 11. 

 Meek, 1877 : King's U. S. Geol. Expl. lOtli Par., Vol. IV, p. 38, PL I, figs. 7, la; 

 PL III, fig. 6. White, 1880: Second Ann. Eept. Indiana Bureau Statistics and 

 Geology, p. 502, PL V, figs. 7, 8, 9. Walcott, 18S4 : Mon. IT. S. Geol. Surv., Vol. 

 VIII, p. 150, PL XIV, figs. 6, 6a, 6b. Beecker and Clarke, 1S89: Mem. New 

 York State Mus. Nat. Hist., p. 51, PL IV, figs. 12-20. Hall and Clarke, 1893: 

 Pal. New York, Vol. VIII, Pt. II, p. 165, fig. 153; PL LV, figs. 1-17. Herrick, 

 1895: Geol. Ohio, Vol. VII, PL XX, fig. 7. 



This well-known and universally distributed form needs no further 

 description. It has as yet been identified from but one locality in the 

 Yellowstone National Park, is represented entirely by casts, and is a small, 

 coarsely plicate form, similar to that from the Lockport (often called Niag- 

 ara) limestone, and identified by Walcott from Upper Devonian strata. 



Formation and locality: Three Forks limestone, base of bluff, Little 

 Sunlight Creek; Arnold Hague. Silurian and Devonian throughout the 



world. 



Atrypa missouriensis Miller. 



PL LXVI, figs. 2a, 2b, 2c. 



Atrypa reticularis (var.) Meek, 1877: King's IT. S. Geol. Expl. 40th Par., Vol. IV, 



p. 38, PL III, fig. 6a. 

 Atrypa desquamata Walcott (uon Sowerby), 1S81 : Mou. IT. S. Geol. Surv., Vol. VIII, 



p. 150, PL XIV, figs. 4, 4rt. 

 Atrypa missouriensis Miller, 1894: Eighteenth Ann. Eept. State Geologist of Indiana, 



1893, p. 315, PL IX, figs. 19-21. 



Shell rather small, subcircular, variable in shape. Dorsal and ventral 

 valves moderately and equally convex, finely striate, not at all or only 

 obscurely marked by distant concentric strise, which, moreover, are not 



