HYDBOZOIDS AND CORALS. 123 



the different corallites vary considerably, even in the same 

 specimen, while the tiexuous nature of the several cylinders 

 makes the irregularity all the more apparent. Not unfre- 

 quently the corallites are so close together as to resemble 

 certain forms of Favosites. 



Aulopora gracilis sp. nov. 

 Plate xlv, tig. 8. 



Prostrate expansions of conical tubules which are arranged 

 in long lines, bifurcating or not, the basal end of each succes- 

 sive tabule being given off from near the orificial extremity of 

 the one behind it. Oral portions erect, with the opening about 

 two millimeters in diameter, and expanding rather rapidly at 

 the margin. 



Sorizon and localities. — Lower Carboniferous, Burlington 

 limestone : Hannibal ; Burlington ( Iowa) ; Keokuk limestone : 

 •Boonville (Cooper county ) ; Keokuk ( Iowa ). 



This species approaches nearer than any oihQv A. con ferta, 

 Winchell, from the Hamilton rocks of Michigan. The tabules, 

 however, are stouter, shorter, the oral parts more elevated and 

 the immediate orifice more campanulate than in the Devonian 

 examples. The form is rather widely distributed both geo- 

 graphically and geologically. It is believed that the Burling- 

 ton and Keokuk specimens are identical, and that the form 

 occurring in the Kinderhook is also to be referred to the same 

 species. 



Chsetetes milleporaceus Teoost. 



Plate xiv, figa. 12a-b. 



Chcjetetes milteporaeeus Troost, 1849: (Ms.). 



Chcetetes miWe^oT-acews Edwards & Haime, 1S51 : Monog. Polyp. Foss., 



p. 272. " 

 Chcetetes milleporaceus White, 1877: Geog. Sur. w. 100 Merid., vol. IV, 



p. 98, pi. vi, fig.- 2a. 



Corallum rather large, massive, subglobose ; made up of 

 fine, closely arranged corallites, having a diameter of one-fourth 

 to one-third of a millimeter. 



Horizon and localities. — Carboniferous, Upper Coal 

 Measures : Glasgow. 



