﻿50 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 47 



conspicuous feature; distinguished only by the size of their zocecia, 

 which are somewhat larger than the average. Zocecial apertures, 

 angular to subangular, with rather thick walls, 5 to 6 zocecia in 2 

 mm.; mesopores small, and comparatively few in number; acantho- 

 pores small and seldom well shown at the surface, although when 

 observed they show the usual apical perforation. 



Internal characters. — In vertical sections the striking feature is the 

 absence of diaphragms in both the zocecia and mesopores. In the 

 axial region the walls are thin and wavy, the crenulation being long 

 and not so frequent as in species of Calloporina. With the inception 

 of the mature region, the walls become greatly thickened and con- 

 siderable laminated tissue is developed upon the inner sides. Tan- 

 gential sections show the zocecial walls to be of considerable thickness 

 and to have the characteristic structure of Batostoma. The acan- 

 thopores are seen to be small, few in number, and situated at the 

 junction angles. 



The rather large angular zocecia, thick walls, and few mesopores, 

 and, more satisfactorily, the absence of diaphragms, distinguish this 

 species from otherwise similar associated forms. 



Occurrence. — Xot uncommon in the Richmond formation at Wil- 

 mington, Illinois. Less abundant in the same strata at Delafield 

 and Iron Ridge, Wisconsin. 



Cat. Xos. 43,218, 43,219, U. S. N. M. 



EXPLANATION OF PLATES 



Plate VI 



Monticulipora mammulata D'Orbigny p. 16 



Figs 1,2. Vertical and tangential sections, X 20, of D'Orbigny's type. 



3. Tangential section, X 35, illustrating the peculiar granulose struc- 



ture. 



Fairmount beds, Lorraine formation, Cincinnati, Ohio. 



Monticulipora cleavelandi James p. 16 



4. Vertical section, X 20, showing the wall structure and distribu- 



tion of cystiphragms and diaphragms. 



5. Tangential section, X 20, through a part of the zoarium where 



the cystiphragms were not developed. 



6. Tangential section of a zooecium, X 35. The inner margin of the 



walls is unusually definite in this zooecium. 



.Middle division of Richmond formation, Dutch creek, near 

 Wilmington, Ohio. 



Orbignyella sublamellosa new species p. 19 



7. Tangential sectii »n, X 20. 



8. Vertical section, X 20, passing through two layers of zocecia. 



9. Tangential section, X 40, showing the acanthopores and the wall 



structure with the white median line suggestive of the Hetero- 

 trypidce. 



