15 



within and contracted below the aperture. Surface reticulate 

 in appearance, the cell openings communicating by a groove 

 across the division, and between these are elevated interrupted, 

 both ridges and grooves arranged in concentric lines crossing 

 the cell divisions. The outline of the aperture or cell is rhom- 

 boidal, and in the centre of the bottom is a circular opening 

 communicating with the cylindrical tube below. 



When the surface is worn, it presents a series of round 

 perforations, which are proportionally larger than they appear 

 in unworn specimens simply from showing the diameter of the 

 cell below the contraction. Transverse diameter three -fourths 

 of an inch to two inches, and greatest vertical diameter rarely 

 an inch. This species is far less common than R. Oweni. 



Geological Formation and Locality. — It occurs in the Galena 

 limestone, at Platteville, Wisconsin, Dubuque, Iowa, Galena 

 and Rockford, Illinois. 



RECEPTACULITES FUNGOSUM— Hall. 



Description. — Body very broadly subturbinate or fungiform ; 

 rounded and very convex below, except the broad base of at- 

 tachment ; upper surface deeply concave in the center, convex 

 towards the margin, and curving abruptly at the sides. Cells 

 small, cylindrical, little contracted at the aperture, arranged in 

 radiating curved lines from the center to the center to the 

 periphery and continuing over the sides and base in the same 

 direction. The central cells are vertical, but on approaching 

 the periphery they are curved upwards and inwards ; 'the lat- 

 eral cells are directed horizontally and gradually turning down- 

 wards are again vertical, opening in the opposite direction 

 from those of the center above. 



Surface appearing reticulate from the concentric grooves 

 which connect the cells upon the surface, and the parallel con- 

 centric ridges ; while these are crossed below by the double 

 series of diverging curved lines. 



To conceive of the form of this species, one may fancy an 

 expanded form of R. Oiveni to be bent abruptly over at an 

 inch or two from the center, and the margins drawn together 

 below, forming a base of attachment. 



The greatest diameter of this species, in the specimens ex- 

 amined, is about three inches ; and the greatest elevation 

 from the center of the base to the summit, is one and three- 

 fourths to two inches ; the depth of the central cavity below 

 the plane of the summit being about half an inch. The length 

 of the cells in the thickest lateral portions of the body, is about 

 three-fourths of an inch. 



