510 BT ill n\. \n EU .1 M «»i COMPARATIVE E06l 



1 1 u.\i wi i.i.\ \i \« biob Sardeson). 



Orihii macrior Sardeson, Bull. Minn. aoad. soi., 1892, 3, p, 330, pi. •">, fig. 5-7. 

 Orthis (DalmoneUa) teetudinaria var. emncrnin WinoheU :ui<l Bchuchert, 



Geoi Mmn., 1893, 3, pt. 1, p. 445, pi. 33, fig. 23 24. 

 Orthis emacerata Sardeson, Amer. geol., L897, 19, p. 102, pi. 5, fig. 14-18, 28. 



Shells subquadrangular, broadest at or Qear the binge, nearly as 

 long as wide. 



Pedicle-valve convex; brachial nearly flat; concentric lim-^ some- 

 times present. A single median plication is prominent near the pedi- 

 cle-beak. The median fold grows wider and higher toward the 

 anterior margin and is hounded by depressed areas. 



The brachial-valve has a corresponding depression, and the stria- 

 tums resemble those of D. rogata Sardeson. There is a total lack of all 

 minuter surface markings. 



Typical specimens measured: — 



Length \\ iilth Greatest convexity 



11 mm. 12.5 mm. 4.5 mm. 



11 mm. 13 mm. 5 mm. 



9 mm. 10.5 mm. 4.5 mm. 



13 mm. 15 mm. 5 mm. 



6 mm. 7.5 mm. 3 mm. 



The common Dalmanella found in the Maquoketa at Clermont has 

 usually been called D. emacerata, but differs from it in having a deeper 

 sinus and more pronounced fold, and in Inning the lateral margins 

 more nearly parallel. Sardeson's name for the species may therefore 

 be revived although he himself did not use it in his second paper. 



Locality: — Maquoketa in Minnesota; Lower Maquoketa at Cler- 

 mont, Iowa. 



Dalmanella corpulent A (Sardeson). 



Orthis corpidcnta Sardeson, Bull. Minn. acad. nat. sci., 1892, 3, p. 330, pi. 5, 

 fig. 8-10. Amer. geol., 1897, 19, p. 107, pi. 4, fig. 11-19. 



Orthis (Dalmanella) testudinaria var. meeki Winchell and Schuchert (non 

 Miller), Geol. Minn., 1893, 3, pt. 1, p. 445, pi. 23, fig. 25-29. 



A few r specimens appear to belong to this species, wdrich is common 

 in the Maquoketa of Minnesota but unknowm elsewhere. The hinge 

 is short, the form subcircular in neanic but rather elongate in adult 

 specimens, the median fold is not strongly delineated, and the sinus 



