BRYOZOA. 517 



to the wearing away of the intermediate spaces. Diagonally 

 they are about 5 mm. apart, measuring from center to center. 

 The zooecia are similarly arranged, about ten in 5 mm., with 

 comparatively large sub-ovate apertures, about 0.35 mm. in 

 diameter, separated by thin interspaces. In better preserved 

 specimens the apertures would probably be smaller and the in- 

 terspaces correspondingly thicker. 



The species must be closely related to G. megastoma, of the 

 Keokuk group. 



Position and locality: Burlington limestone. Sagetown, Hen- 

 derson Co., 111. 



GLYPTOPORA KEYSERLINGI Prout. 



PI. LXXVni, fig. 4-4b. 



Coscinium keyserlingi Prout, 1858. Trans. St. Louis Acad Sci. vol. I. p. 269, PI. XV 



fig. 4-4a. 



? Coscinium wortheni Prout, 1860. Ibid vol. I, p. 571. 



1 Coscinium wortheni Prout, 1866. Geol. Surv. El. vol. 2, p. 412, PI. XXTT, fig. l, la. 



The complete zoarium consists of thin upright bifoliate ex- 

 pansions, arranged in such a manner that they enclose large 

 and rapidly expanding hexagonal cups. The under side of the 

 dome-shaped or flattened base is covered with a wrinkled epi- 

 theca, and the bifoliate fronds which extend up from it are 

 equivalent to the ridges in G. micheliniti. At the angles of 

 junction of the fronds, which vary in thickness from 0.25 to 

 1.0 mm., there is a narrow depressed solid strip on each side, 

 making the junction very frail. In consequence it is only in ex- 

 tremely rare instances that the foliate expansions are found 

 joined together, and in nine cases out of ten we deal only with 

 fragments of one of the sides or partitions of the cups. Figure 

 4 represents a small but nearly complete side, and shows the 

 form and distribution of the lanceolate or acutely elliptical 

 dimples and zooecia. Its width is comparatively greater than 

 usual, the angle formed by the two non-poriferous edges being 

 a little over 90. In other examples the angle varies from that 

 degree down to 50. The dimples are from 4 to 6 mm. long, 

 1.5 to 2.0 wide, and generally a little the widest in their upper 

 half, and somewhat acutely terminated below. Their surface as 



