508 bulletin: museum of comparative zoology. 



anterior margin in large specimens. In some eases the exterior of 

 this valve is marked by fine concentric striations. 

 A typical specimen measured : — 



Width 27 mm., Length 26.5 mm., • Greatest convexity 13 mm. 



Locality: — Richmond at Spring Valley and Granger, Minnesota; 

 Delafield, "Wisconsin; Savannah, Illinois; Clermont, and Lattners, 

 Iowa. M. C. Z. 8,535. 



Hebertella sinuata (Hall). 



Orthis sinuata Hall, Pal. N. Y., 1847, 1, p. 128, pi. 32B, fig. 2. Miller, Cine. 



quart, journ. sci. 1875, 2, p. 36. 

 Orthis occidentalis var. sinuata Meek, Pal. Ohio, 1873, 1, pt. 2, p. 98. 

 Hebertella sinuata Hall and Clarke, Pal. N. Y., 1892, 8, pt. 1, p. 222, pi. 5A, 



fig. 1-8. Hayes and Uhich, Folio 95 U. S. G. S. illus. sheet, 1903, fig. 17. 



Cmnings, Amer. journ. sci., 1903, ser. 4, 15, p. 34, footnote. Foerste, 



BuU. sci. lab. Denison univ., 1910, 16, p. 52, pi. 2, fig. 5. 

 Hebertella occidentalis sinuata Schuchert, Bull. 87, U. S. G. S., 1897, p. 229. 



Cumings, 32nd Ann. rept. Dept. geol. nat. res. Indiana, 1908, p. 908, pi. 



34, fig. 3-3e. 



Hebertella sinuata differs from //. occidentalis in the absence of the 

 slight median depression near the beak of the pedicle-valve of the 

 latter. This species is very common throughout the Richmond, and 

 everywhere shows great similarity to H. occidentalis. The primary 

 striations are coarser than those of the latter, but all intermediate 

 stages can usually be found. 



Since all the specimens from the Upper Maquoketa at Brainerd, 

 Iowa, were coarsely striated, no differentation of two forms was in- 

 dicated. 



Length Width Convexity 



30 mm. 40 mm. 25 mm. 



32 mm. 36 mm. 21 mm. 



16 mm. 29 mm. 15 mm. 



Locality: — Mays\'ille and Richmond; southern Ohio; Kentucky; 

 Tennessee; Indiana; Iowa, etc. 



Hebertella clermontensis, sp. nov. 



Plate 1, fig. 3. 



Shell small, length about four fifths of the width, with slight indi- 

 vidual variation. Hinge-line a trifle less than the middle width of 



