314 BRAXSOX AXD GREGER— AMSDEX FORMATIOX OF WYOMIXG 



BRY0Z0AN8 



A few fragments too imperfect for generic reference were collected; 

 one group is fenestelloid and another batastomelloid in appearance. 



OBBICULOIDEA WY0MINGEN8IS n. sp. 

 Plate 19, figures 7 aud 8 



Cotypes three specimens from Bull Lake Creek. Shell subcircular in 

 outline ; brachial valve with apex about one-fourth the diameter from the 

 posterior margin; surface in front of apex parallel to plane of valve for 

 about one-half the diameter of the shell, thence sloping gently to the 

 anterior margin. Laterally from the apex the sides are gently concave, 

 behind the apex strongly concave. Surface marked by ordinary, concen- 

 tric lines of growth, 2 to 3 to the millimeter. Pedicle valve with apex a 

 short distance anterior to the center of the shell. Shell slightly convex. 

 Delthyrium extending from apex three-quarters of the distance to the 

 posterior margin of the valve; gradually narrowing posteriorly; com- 

 pletely closed by the listrium. Lines of growth like those on the brachial 

 valve. Diameter of the larger specimen about 25 millimeters, of the 

 smaller specimens 15 millimeters and 16 millimeters. 



0RTH0TETE8 KA8KA8KIEN8I8 (McCliesney) 

 Plate 19, figures 3 and 4 



1860. Orthis kaskaskiensis McChesney, Descriptions of New Paleozoic Fossils, 

 page 31. 



1892. Derhya kaskaskiensis Hall and Clark, Paleontology of New York, volume 

 8, part 1, plate 11&, figure 6. 



1914. Ortliotetes kaskaskiensis Weller, Monograph 1," Illinois Geological Sur- 

 vey, page 77, plate 6, figures 1-14. 



1916. Orthotetes kaskaskiensis Weller, Contributions from Walker Museum, 

 volume 1, number 10, pages 245-246, plate XVI, figure 1. 



The specimens of this species from the Amsden are slightly larger than 

 examples from the Pella beds of Fort Dodge, Iowa. They agree more 

 fully with specimens from the Saint Louis oolite of Lewis County, Mis- 

 souri. The two specimens in the collection measure: Length, 30 milli- 

 meters ; breadth, 43 millimeters ; and length, 32 millimeters ; breadth, 46 

 millimeters. 



DIAPHRAGMU8 PHILLIP8I (Norwood and Pratten) 



Plate 19, figures 5-6 



1854. Prodiictus phillipsi Norwood and Pratten, Journal of the Academy of 

 Natural Science of Philadelphia, volume 3, second series, page 8, 

 plate 1, figures 2 a, 1) and c. 



« Synonomy given by Weller in tlie Illinois monograpli is not repeated in this paper, 

 but the original reference is given. 



