LOWER CARBONIFEROUS FOSSILS. 547 



Gallatin Range; north of Bighorn Pass, Gallatin Range; A. C. Grill. 

 Cherty belt, Bighorn Pass, Gallatin Range; J. P. Iddings. Crowfoot 

 Ridge, Gallatin Range, bed 24 ; A. C. Gill. North of Owl Creek, northeast 

 slope of Teton Range ; W. H. Weed. North side of south fork of Mill 

 Creek, Snowy Range; Louis V. Pirsson. Slide, east side of Gallatin 

 River, below Fan Creek. Kinderhook age, Burlington, Iowa; Hamburg, 

 Illinois; Sciotoville, Ohio. 



SPIRIFER Sowerby, 1815. 



Spirifer ckntronatus Winchell. 

 PL LXX, figs. 3a, 3b, 3c, 3d, 



Spirifer centronatus Winchell (A.), 1865: Proc. Acad. Nat. Sci. Philadelphia, p. 118. 



White, 1875: Wheeler's Expl. Surv. W. 100th Merid., Vol. IV, p. 86, PI. V, 



figs, 8a-8e. 

 Spirifera centronata Hall and Whitfield, 1877: King's U. S. Geol. Expl. 40th Par., Vol. 



IV, p. 254, PI. IV, figs. 5, 6. 



Spirifer centronatus is by far the most abundant and universal form in 

 the Yellowstone National Park. It has been identified at nearly every 

 locality from which collections have been made, and appears often to have 

 been present in large numbers. The species is already known in the Rocky 

 Mountain region from the reports of C. A. White and of Hall and Whit- 

 field. I have compared my material with their types, and also with specimens 

 from the Waverly rocks of Richfield, Ohio, and all are without doubt 

 specifically identical. 



Spirifer centronatus usually develops four ecpial plications on the fold 

 and three in the sinus, with sixteen or more (usually) simple plications on 

 the. wings. The hinge line is always the widest portion of the shell. The 

 anterior outline is curved, with a tendency to become quadrate. In other 

 words, the shape is sometimes that of the smaller segment of a circle, 

 sometimes more tumid below, with angular or mucronate extension at the 

 hino-e line. Always transverse. Area of the ventral valve not very broad; 

 beak incurved, small. Sinus beginning at the extremity of the beak. It is 

 there relativelv deep, and sharply defined on either side by a prominent 

 plication, but grows broader and shallower, somewhat losing definition 

 below. Subsequently a central rib develops in the sinus, and this is at 

 about the same time supplemented by two others, one on either side, 



