524 bulletin: museum of comparative zoology. 



The brachial-valve is well rounded in the posterior region; the 

 median fold becomes evident half-way to the anterior margin where 

 it finally is well defined. The fold bears 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 mnbonal region, which is smooth. 



Width Length Greatest convexity 



15 mm. 12 mm. 10 mm. 



In general, this representative of Parastrophia closely resembles 

 the type from Wilmington, but differs in haAdng 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 Comrad, Journ. Acad. nat. sci. Phil., 1842, 8, p. 264, pi. 14, fig. 21. 

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



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

 13k-13y. Billings, 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. 



Rhynchonella increhescens Hall (part) Geol. Wise, 1862, 1, p. 123, pi. 11, fig. 2. 



RhynchoneUa 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. 

 Wise, 1882, 4, p. 263, pi. 12, fig. 26, 27. ChamberHn, ibid., 1883, 1, p. 

 155, fig. 30. Keyes, Missouri, Geol. surv., 1895, 5, p. ^9, pi. 41, fig. 12. 



Rhynchotrema capax WincheU 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. rept. 

 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 



