476 PALAEONTOLOGY OF ILLINOIS. 



rocks. In the Upper Silurian rocks; however, the genus is re- 

 presented by at least ten species, in Devonian by from twenty 

 to thirty, in Lower Carboniferous by perhaps an equal number, 

 and terminates its existence in the Coal Measures, with five or 

 six species. The total number of valid species known to me 

 from American rocks alone is not less than seventy, while four- 

 teen species are recorded from European deposits. 



FISTULIPORA COMMUNIS Ulrich. 



PI. XL VII. fig. 1, la. PI. XL VIII, fig. 1, la. 



Zoarium explanate, commonly attached to foreign bodies, at 

 other times free and provided with an epitheca, often composed 

 of layers, each a mm. or two in thickness. The surface is raised 

 into low, broad, rounded monticules two or three mm. wide, 

 and their summits three or four mm. apart. Apertures circular 

 with a very thin but distinctlv elevated peristome, generally 

 about 0.16 mm. in diameter, but attaining a diameter of 0.25 

 mm. near the summits of the monticules; distances apart rather 

 variable, those in the monticules more separated than the others. 

 In the intermediate spaces five or six occur in two mm. When 

 the surface is worn the apertures appear quite small and the 

 interspaces very wide. Zooecia thin walled, circular or oval, 

 provided with two or three distant diaphragms. Lunarium ob- 

 solete. Vesicles thin-walled, generally wide and shallow, about 

 two-thirds as wide as the zocecia, surrounding them in two or 

 more series and forming large clusters under the monticules. 

 In good tangential sections the vesicle spaces exhibit one or 

 more subcentral minute spots, which probable represent perfor- 

 ations in their covers. 



This very abundant species was at first supposed to be the 

 F. minuta of Rominger, but from an examination of authentic 

 specimens of that species, it appears that his species is closely 

 allied to Liocleina occidens (H. & W. sp.) and not a Fistuli- 

 pora at all. The small zooecia, their circular form, and the 

 obsolete lunarium, distinguish F. communis from the associated 

 species. 



Position and locality: Hamilton group. Buffalo, Iowa, and 

 Rock Island, 111. 



