464 THE PALEONTOLOGY OF MINNESOTA. 



[Rhynchonella tf) anticostiensis. 



Formation and locality. A very characteristic and common species of the upper portion of the 

 Hudson River group; a few specimens have also been secured from the upper portion of the Galena, which 

 as far as can be determined, are referable to this species. In the Hudson River group at Spring Valley 

 and Granger, Minnesota; Graf, Iowa; Iron Ridge, Stockbridge and near Clifton, Wisconsin: Wilmington, 

 Illinois; near Cape Girardeau, Missouri; Ohio; Indiana; Kentucky, and Anticosti. In the Galena near 

 Cannon Falls and near Rochester, Minnesota. 



Collectors John Kleckler, M. W. Harrington, W. H. Scoflelrt and the writers. Also in the colli-ci inn 

 of Dr. C. H. Robbins, of Wykoff, Minnesota. 



Mus. Reg. No. 177, 4092, 4095, 5547, 8196-8199. 



RHYNCHONELLA (?) ANTICOSTIENSIS Billings. 



FIG. 34. Rhynchonella anticostiensis Billings, a, 6, c, different views of a specimen. From "Palaeozoic 

 fossils of Canada." p. 142. 



1862. Rhynchonella anticostiensis BILLINGS. Palasozoic Fossils, vol. i, p. 142, flg. 119A-C. 



1863. Rhynchonella anticostiensis BILLINGS. Geology of Canada, p. 211, flg. 212. 



Compare with Rhynchonella argenturbica WHITE. Report of the U. S. Geological and Geographical 



Survey west of the 100th Meridian, vol. iv, p. 75, pi. iv, flg. 12. 



Original description : " Subpentagonal ; apical angle about 80 ; side nearly straight 

 or slightly convex for rather more than half the length from the beak, then curving 

 to the edge of the mesial sinus; front nearly straight for the breadth of the sinus; 

 side view oblong; front, dorsal and ventral sides nearly straight; umbo of dorsal 

 valve abruptly curved in to the base of the beak of the ventral valve, which is 

 conical, erect and scarcely incurved. Ventral valve with a deep mesial sinus, 

 becoming obsolete at two-thirds the length from the base; dorsal valve with a 

 strong mesial elevation which, on approaching the umbo, disappears and is succeeded 

 by a scarcely perceptible sinus, which continues to the summit. Surface with 

 eighteen or twenty radiating angular ridges, crossed by close zigzag imbricating 

 striae; three ribs in the ventral sinus and four on the dorsal mesial elevation." 



The more or less erect beak of the ventral valve, and the conspicuous deltidial 

 plates of E. anticostiensis, remind one much of species of Rhynchotreta Hall. This 

 form is distinguished from R. neenah Whitfield by its greater triangular outline and 

 in the four continuous plications of the less elevated median fold. 



Formation and locality. Common in the upper beds of the Hudson River group at Wilmington and 

 Savannah, Illinois; Graf, Iowa; Wisconsin, and English Head, Anticosti. 



Collector. C. Schuchert. 

 Mus. Reg. Nos. 8201-8203. 



