DESCRIPTION OF SPECIES BRYOZOA 291 



median line of the branches the lunaria are situated on the outer lateral 

 margins of the zocecial apertures, and the apertures themselves are 

 directed with a slight obliquity toward the median line. 



The dimensions of an average example are: Width of branches of 

 zoarium, 4 to 5 millimeters; greatest thickness of branches, .75 milli- 

 meter to 1 millimeter; number of zocecial apertures in the space of 2\ 

 millimeters longitudinally, 3 to 4; number of zocecial apertures in the 

 space of 2 millimeters transversely, about 4. 



Remarks. — This species is one of the less common bryozoa in the Fern 

 Glen fauna. The species is usually identified from a somewhat higher 

 horizon, being an abundant form in the Upper Keokuk, Salem, and Saint 

 Louis faunas, but the Fern Glen examples agree more closely with the 

 original description of the species than do those commonly so identified 

 from the Salem and Saint Louis. 



EVACTINOPORA SEXRADIATA M. & W. 



Plate 15, figures 5-16 



1868. Evactinopora sexradiata Meek and Worthen, Geological Survey of Illi- 

 nois, volume 3, page 502, plate 17, figure 3. 



1890. Evactinopora sexradiata Ulrieh, Geological Survey of Illinois, volume 3, 

 page 510, plate 73, figures 2-2&. 



1894. Evactinopora sexradiata Keyes, Missouri Geological Survey, volume 'o, 

 page 18. 



Description. — Zoarium free, with a stellate base, which is the only por- 

 tion yet detected in the Fern Glen collections. Base with from four to 

 nine rays, six being the most usual number; the rays are compressed 

 laterally, their lower edge describing a convex curve from the center of 

 the base to the tips of the rays; sinuses between the rays more or less- 

 variable in depth, the central disk varying from one-fourth to one-half 

 the total diameter of the base. In the center of the lower side of the 

 disk a small polygonal area is often present, outlined by faint ridges, the 

 angles of the polygon being equal in number to and opposite the rays, 

 and from each angle a similar ridge passes to the extremity of the ray 

 along its median line ; the size of the central polygon varies with the rela- 

 tive size of the disk as compared with the total diameter of the base ; in 

 other individuals the ridges marking the rays join at the center of the 

 disk in a regular or irregular manner without the polygonal inclosed 

 area. 



The diameter of an average sized individual is 11.5 millimeters; the 

 diameter of the largest example observed is 20 millimeters. 



