520 bulletin: museum of comparative zoology. 



Minnesota. All are shorter than those in Professor Schuchert's 

 collection, and the anterior margins are less pointed. Very slight 

 wrinkling is discernible on the valves near the hinge-line, and in one 

 specimen is almost obsolete. 



The striae are more distinct on the brachial- than on the pedicle- 

 valve; clearly alternating, usually three or four, rarely two or five, 

 finer between two coarser ones. The finer striae vary in intensity 

 and in places are undulatory ; the coarser in all cases are less erratic 

 than the finer. Seven or eight of the prominent ones are counted in 

 5 mm. at the anterior margin. 



One specimen has dimensions as follows : — Width along hinge-line, 

 28.5 mm.; across middle, 24 mm.; length of pedicle-valve, 20.5 mm.; 

 of the brachial, 20 mm. ; greatest convexity, 8 mm. at 13.5 mm. from 

 the beak; height of cardinal area, 3.5 mm. This represents the 

 medium of the three specimens. The largest had a width at the 

 hinge of 37.8 mm. and length of pedicle-valve of 23 mm. The smallest 

 had width at hinge 21.2 mm., and length of pedicle-valve 16.2 mm. 

 A specimen from the type-locality measured by Foerste corresponded 

 nearly to the fu-st cited above, the main difference being a length of 

 pedicle-valve greater by 1.2 mm. in the type. 



Locality: — Riclmiond (Maquoketa); Spring Valley, Minnesota, 

 and Clermont, Iowa. M. C. Z. 8,539. 



Strophomena nutans Meek. 



Strophomena {Hemipronites) nutans Meek, Pal. Ohio, 1873, 1, pt. 2, p. 77, pi. 6, 



fig. 1. 

 Hemi'pronites nutans Miller, Cine, quart, journ. sci., 1875, 2, p. 46. 



Streptorhynchus nutans Miller, N. A. geol. pal, 1889, p. 378. 



Strophomena nutans HaU and Clarke, Pal. N. Y., 1892, 8, pt. 1, p. 251, pi. 8, 

 fig. 11; pi. 9A, fig. 5-7; pi. IIA, fig. 6, 7. Foerste, Amer. geol, 1903, 31, 

 p. 338. Cumings, 32d Ann. rept. Dept. geol. nat. res. Indiana, 1908, 

 p. 936, pi. 38, fig. 5-5e. Foerste, Bull. sci. lab. Denison univ., 1912, 17, 

 p. 68, pi. 3, fig. 2a-e; pi. 9, fig. 15; pi. 10, fig. 2a-c; pi. 3, fig. 2 b; pi. 11, 

 fig. 8; pi. 10, fig. 3a-d; pi. 9, fig. 16. 



Several specimens of Strophomena nutans were found in the Lower 

 Maquoketa four miles west of Clermont. They were all smaller than 

 S. concordcnsis described by Foerste; but it is possible that he would 

 call these forms depauperate gerontic examples of that species. The 

 largest has a width of 28 mm., a length of 23.5 mm., and a greatest 

 convexity of 10.5 mm. The average specimen measures 21 mm. in 



