508 bulletin: museum 01 comparative eo5logy. 



anterior margin in lai pecimer . In iomi the exterior of 



this valve is marked bj fine concentric striatiori . 

 A typical specimen measured: — 



Width 27 mm., Length 26.5 mm., Greateel convexity 13 mm. 



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

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

 Iowa. M. ('. Z. 8,535. 



Hebertella sim ata (Hall). 



Orthis sinuata Hull, Pal. X. V., 1847, 1, p. 128, pi. 32B, dg ; 2. Miller, Cine. 



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

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

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



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



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



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

 Hebertella occidental is 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 //. 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 difl'erentation 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 ville 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 w T idth of 



