428 THE PALEONTOLOGY OF MINNESOTA. 



[O.'gennanB. 



The specific name is after A. D. Meeds of the University of Minnesota. 



Associated with the above species, at its climax of development in number of 

 individuals, a very characteristic and striking variety makes its appearance, which 

 is named germana. 



Formation and locality. Rare near the base of the Galena shales at St. Paul, Minnesota,- and 

 McGregor, Iowa, a few feet above the horizon of O. pectinella and variety sweentyi. It becomes a common 

 and very characteristic fossil in the beds immediately above, and is there associated with Clitambonites 

 diversa Shaler; it is known to extend for thirty feet above this horizon. 



The following are the most prominent localities at which this species has been collected: Cannon 

 Falls, Kenyon, Warsaw, Fountain and Preston, Minnesota: Decorah and McGregor, Iowa; Neenah and 

 Oshkosh, Wisconsin. 



Collectors. W. H. Scofleld, E. O. Ulrich and the writers. 

 Mus. Reg. Nos. 4055, 5860, 5861, 6746, 7771-7785. 



Variety GERMANA W. and S. 



PLATE XXXII. FIGS. 43-45. 



1892, April 1. Orthis meedsi var. germana W. and S. American Geologist, vol. ix, p. 290. 



This variety is distinguished from 0. (D.) meedsi by the following characters: 

 Smaller in size and squarer in outline; valves more strongly and more evenly 

 convex; hinge areas nearly equal in width and narrower, with the beak of the 

 ventral valve slightly elevated above that of the dorsal; ventral valve with a slight, 

 somewhat angulated fold, while the dorsal has a shallow, but distinct sinus origin- 

 ating immediately below the apex of the valve. The fold and sinus produce a slight 

 sinuosity in the anterior margin, the direction of which is just the reverse of that in 

 0. (D.) meedsi. 



The largest specimens of this variety observed have the general external expres- 

 sion of small individuals of Orthis subquadrata, and no external nor internal parts 

 are known that preclude the form from being viewed as the ancestor of that species 

 which attains its specific development in the upper portion of the Cincinnati group 

 The beds from which var. germana is obtained are fully one hundred feet below those 

 holding 0. subquadrata. During this interval no specimens of Dinorthis have as yet 

 been detected. 



Formation and locality. Not rare in the upper part of the Galena shales at several localities south 

 of Caunon Falls, near Kenyon and Fountain, Minnesota. This horizon is also characterized by Anastro- 

 phia hemiplicata and a number of small Bryozoa. 



Collectors. W. H. Scofleld and the writers. 

 Mus. Reg. No. 7770. 



ORTHIS (DINORTHIS) SUBQUADRATA Hall. 



PLATE XXXII, FIGS. 46-50. 



1847. Orthis subquadrata HALL. Paleontology of New York, vol. i, p. 126, pi. xxxnA, flg. 1. 

 1862. Orthis subquadrata HALL. Geology of Wisconsin, vol. i, p. 54, flgs. 1, 2. 

 ^1863. Orthis subquadrata BILLINGS. Geology of Canada, p. 105, flg. 146. 



