BULLETIN: MUSEUM 01 COMPARATIVE EOdLOOT. 



The brachial-valve is \wll rounded in the po terioi region; the 

 median t" «. > 1 * I becomes evident half-way t«» the anterior margin where 

 it finally is well defined. The fold bean four plications; each 

 lateral slope bears two. The type-specimens from Wilmington have 



from three tO five plications on the median fold and three on each 



lateral slope. All plications, and also the fold and sinus fade away 

 in the umbonal region, which is smooth, 



Width I.eugth Greatest convexity 



15 mm. 12 mm. 10 mm. 



In general, this representative of Parastrophia closely resemhl»s 

 the type from Wilmington, but diti'ers in having fewer plications and a 

 lesser convexity. 



Locality: — -Maquoketa (Fernvale) at Wilmington, Illinois, and 

 Lower Maquoketa at Clermont, Iowa. 



Rhynchonellidae. 

 Rhynchotrema cap ax (Conrad). 



Atrypa capax Conrad, Journ. Acad. nat. sci. Phil., 1842, 8, p. 264, pi. 14, fig. 21. 

 Hall, Amor, journ. sci., 1844, 47, p. 109. 



Atrypa increbescens Hall (part), Pal. N. Y., 1847, 1, p. 146, pi. 33, figs. 131, 

 13k-13y. Hillings, Can. nat. geol., 1856, 1, p. 207, fig. 15, 16. Hall, 

 13th Kept. N. Y. state cab. nat, hist., 1860, p. 66, fig. 6, 7, 9-11. 



Rhynchonelln increbescens Hall (part) Geol. Wise, 1862, 1, p. 123, pi. 11, fig: 2. 



Rhynchonella capax Billings, Geol. Canada, 1863, p. 211, fig. 213. Safford, 

 Geol. Tennessee, 1869, p. 275, fig. 4-6. Meek, Pal. Ohio, 1873, 1, pt. 2, 

 p. 123, pi. 11, fig. 2. Miller, Cine, quart, journ. sci., 1875, 2, p. 17. 

 Roemer, Leth. Geog., 1, Leth. Pal. Atlas, 1876, p. 4, fig. 13a. White, 2d 

 Ann. rept. Indiana bur. state geol., 1880, p. 489, pi. 1, fig. 9-11. 10th 

 Rept. state geol. Indiana, 1881, p. 121, pi. 1, fig. 9-11. Whitfield, Geol. 

 \Yisc, 1882, 4, p. 263, pi. 12, fig. 26, 27. Chamberlin, ibid., 1883, 1, p. 

 155, fig. 30. Keyes, Missouri, Geol. surv., 1895, 6, p. 99, pi. 41, fig. 12. 



Rhynchotrema capax Winehell and Schuchert, Geol. Minn., 1893, 3, pt. 1, p. 462, 

 pi. 34, figs. 30-34. Hall and Clarke, Pal. N. Y., 1893, 8, pt. 2, p. 183, 185, 

 pi. 56, fig. 14-18, 20-27; pi. 83, fig. 31. Whiteaves, Pal. foss. Canada, 

 1895, 3, pt. 2, p. 121; 1897, 3, pt. 3, p. 178. Cumings, 32d Ann. sept. 

 Dept. geol. nat. res. Indiana, 1908, p. 931, pi. 36, fig. 6-6h. 



This well-known species is quite plentiful in several exposures of 

 the Lower Maquoketa at Clermont, Iowa. The shell is of medium 

 size, and varies greatly in shape with age. Some mature specimens 



