152 



large zooecia and mesopores, elevated above, or depressed slightly below 

 tbe general level of the surface. About 9 maculoe in 1 sq. cm. Mesopores 

 abundant at the surface, frequently entirely surrounding the zocecia ; at 

 other times not conspicuous. Zocecial apertures round, and regular in size. 

 Acanthopores, in unweathered specimens, appearing at the surface as 

 large blunt spines at the angles of the zooecia, and giving to the surface 

 a decidedly spinose appearance. The zooecia average 7 in 2 mm. 



In tangential sections the zocecia are tliick-walled and round. The 

 angles between the zooecia are filled witli secondary sclereneliyma and 

 acanthopoi'es. Mesopores usually aliuinl.int, Imt nearly absent in some sec- 

 tions. Acanthoi>ores numerous, 4 to 10 surrounding a zocecium ; large and 

 thicli-walled, with a small distinct central canal ; sometimes indenting the 

 zocecial walls. No intermural lamina. Connnnnication pores usually ab- 

 sent, but numerous in some sections. 



In longitudinal sections the zoo'cia are thin-walled and wavy in the 

 axial region, and usually without diaphragms. Diaphragms begin ab- 

 ruptly as the mature region is entered, and become numerous toward the 

 surface, where they are from one-half to one tube-diameter apart. Zocecial 

 walls much thickened in the mature region, and proceeding directly to 

 the surface, where they emerge at right angles to the latter. In immature 

 specimens the zocecial apertures are oval, the mature region shallow, and 

 the zocecia emerge obliquely to the surface. In the longitudinal section 

 the acanthopores are thick-walled, with a small central canal, crossed by 

 an occasional diaphragm. The diaphragms in the zooecia are usually 

 straight, but are occasionally cystoid. Diaphragms are more numerous in 

 the mesoix>res. 



The distinguishing features of Batostoma prosso-i are the ramose 

 growth, numerous mesopores and large acanthopores. The species is named 

 in honor of Professor C. S. Prosser of Ohio State University. It occurs 

 in the upper 40 feet of the Waynesville, and commonly in the lower 20 

 feet of the Liberty, at Wei-sburg, Indiana. It disappears abruptly at the 

 level of the Plectamhonites sericcus layer, as does also B. vatiajis, with 

 which it is associated. 



