674 PALEONTOLOGY OF ILLINOIS. 



Position and locality: Keokuk group. Warsaw and Nauvoo, 

 111. 



PROUTELLA Ulrich. 



(For generic diagnosis see page 403.) 



This genus approaches very near to some of the CHILOSTO- 

 MATA, but agrees with the CRYPTOSTOMATA in having the zooecia 

 layers follow each other in direct sequence so as to form tubes. 

 Proutella furnishes a powerful argument in favor of the view 

 published in my "American Palaeozoic Bryozoa" as to the func- 

 tions or purpose of diaphragms. 



PROUTELLA DISCOIDEA Prout. 



PI. LXIX, fig. 4-4d. 

 Cyclopora discoidea Prout, 1860. Trans. St. Louis Acad. Sci., Vol. 1, p. 578. 



Cyclopora discoidea Prout, 1866. Geol. Surv. 111., Vol. II, p. 420, PI. XXII, fig. 10- 

 lOa, and PI. XXI, fig. 2-2a. 



Zoarium a thin sub-circular expansion, several cm. in diame- 

 ter, and less than 1 mm. in thickness. Lower or epithecal sur- 

 face convex, with a short peduncle at the center, and around it 

 more or less strong concentric undulations or sharp wrinkles; 

 crossing these there are fine radiating stria', which correspond 

 with the arrangement of the zooecia, as is shown by the appli- 

 cation of moisture, when the oblong procumbent portion of the 

 zooecia is brought to view. Upper or celluliferous surface more 

 or less concave, with the rhombic or hexagonal zocecia arranged 

 in very regular curved intersecting lines, about nine in three 

 mm. Apertures a little oblique, rounded or sub-rhomboidal, 

 about 0.28 mm. in diameter, of nearly uniform size throughout; 

 occasionally preserving a delicate membrane, which closes some- 

 what more than one-half of the opening, the orifice left being 

 sub-triangular in form and situated at the anterior or depressed 

 side of the aperture. Interspaces ridge-like, with the angles a 

 little elevated. As shown by vertical sections, the short zooecial 

 tubes run from the basal membrane to the upper surface with 

 a gradual curve, without, however, becoming direct at the aper- 

 tures. According to the thickness of the expansion, each tube 

 exhibits from one to four incomplete diaphragms, which spring 



