PROTOZOANS AND SPONGES. 103 



Receptaculites oweni Hall. 



Plate xil, flgs. la-b. 



Cosinopora sulcata Owen, 1844 : Geol. Expl. Iowa, Wigconsin and Illinois, 



p. 40, pi. vii, fig. 5. (Not Goldfuss.) 

 Receptaculites oioeni Hall, 1851 : Geol. riur. Wisconsin, Rept. Prog., p. 13. 

 Receptaculites oiveni Hall, 1862: Geol. Sur. Wisconsin, p. 46, fig. 3. 

 Receptaculites oweni Meek and Worthen, 1868: Geol. Sur. Illinois, vol. 



Ill, p. 802, pi. ii, fig. 3. 

 Receptaculites oweni Whitfield, 1882: Geol. Sur. Wisconsin, vol. IV, p. 239, 



pi. x,fig.7. 



Very large, forming broad, discoidal expansions, from two 

 or three to twenty or more inches in diameter; very thin cen- 

 trally, but greatly thickened toward the margins. " The sub- 

 stance of the fossil is filled with circular, cell-like perforations, 

 placed perpendicular to the plane of the disk, and arranged in 

 curved or concentric lines or rows, which radiate or diverge 

 from a central point, and the cells gradually increase in dimen- 

 sions as they approach the margin of the disc; but with fre- 

 quent intercalated rows. The cells are arranged so as to form 

 circular and often direct radiating lines, as well as the concen- 

 trically curved lines above mentioned. Cell apertures on the 

 lower side, nearly as large as the body of the cell within, with 

 the margins excavated or flaring, forming sharply angular sur- 

 faces on the partition walls; but on the upper surface they are 

 contracted to about half the diameter of the tube within, and 

 the aperture is rhombic or quadrangular, with walls, which are 

 variously ornamented according to the condition of preserva- 

 tion and the compactness of the arrangment." ( Whitfield.) 



Horizon and Localities. — Lower Silurian,Trenton limestone : 

 Jefferson, Pike and Saint Louis counties. 



