484 PALEONTOLOGY OF ILLINOIS. 



arrangement around the zooecia. As they approach the surface 

 the floor of the vesicles (the top of the underlying one) is cov- 

 ered with a deposit of light colored sclerenchyma, which ap- 

 pears to be traversed by minute vertical canals. Near the sur- 

 face this perforated deposit entirely fills the vesicles. It is of 

 darker color in the immediate vicinity of the zooecia. In tan- 

 gential sections showing the characters just beneath the surface 

 the zooecia are circular, the vesicles and lunaria unrecognizable, 

 at a deeper level the lunarium is fairly well shown, and the 

 form of the numerous vesicles, though they are still partially 

 filled with the deposit, is readily determinable. At the median 

 plane the zooecia are arranged between longitudinal lines. These 

 sections also show that the interspaces gradually increase in 

 width, w 7 hile the zooecia diameter decreases with growth. Dia- 

 phragms fairly numerous, flat or slightly concave, a tube diam- 

 eter or less distant from each other. 



This fine species need not be confounded with any bryozoan 

 known to me from either the St. Louis or the Chester horizon. 



Position and locality: Near the dividing line between the St. 

 Louis and Chester group, Monroe Co., 111. The species may be 

 found both above and below the line. 



MEEKOPORA APPROXIMATA Ulrich. 



PI. LXXVII, fig. 5. 



Zoarium bifoliate, growing into irregularly undulating thin 

 expansions, from one to one and a half mm. thick. Surface 

 smooth, with small solid maculae, their centers four to five mm. 

 apart. Apertures closely approximated, oblique, sub-circular or 

 subtriagular in outline, 0.20 to 0.30 mm. in diameter, arranged 

 in more or less regular diagonally intersecting rows, seven in 

 three mm. measuring along the rows; interspaces thin, the 

 lower margin of the aperture elevated into a prominent hood. 

 Median lamina? forming a rugosely wrinkled plane from w r hich 

 the zooecial tubes proceed with a gradual curve to the surface 

 which they reach obliquely. Diaphragms usually flat, most 

 abundant in the deeper portion of the zoarium, where also they 

 are often recurved. Lunaria quite angular in tangential sec- 



