18 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 326 



to nine, most commonly six or seven, mesopores associated with each zooecium; 

 maculae consisting of irregularly angular mesopores bordered by zooecia above 

 average in size. Acanthopores absent or extremely minute. 



Longitudinal section. — Zooecia thin-walled throughout length, somewhat 

 inclined in earliest development but rapidly becoming erect. Cystiphragms con- 

 spicuous, commonly extending across half the width, or somewhat farther, of each 

 zooecium, six to 14, generally eight to 11, in 1.0 mm, and commonly lining one 

 side of zooecium only. Diaphragms in zooecia usually less than one zooecial 

 diameter apart, particularly in lower part of zoarium, but in some zooecia may be 

 three or four zooecial diameters apart in upper portion of zoarium. Mesopores 

 closely tabulate, from six to 15, commonly 10 to 12, diaphragms in 0.5 mm. Acan- 

 thopores not observed. 



Remarks. — In all respects except size of zoarium the Spechts Ferry speci- 

 mens agree well with Prasopora simulatrix var. orientalis as described by Ulrich. 

 Representatives of this variety are commonly much larger than specimens described 

 herein; forms under study, however, fall within the size range of the species 

 (Ulrich, 1895, p. 245). The small size of the Spechts Ferry specimens does not 

 necessarily result from unknown ecologic factors, as Fritz (1957, p. 35) reports 

 that this variety attains a subconical form after having passed through discoidal 

 or hemispherical stages. Presumably the Spechts Ferry specimens could represent 

 zoaria in a youthful stage of development. In zoarial form and size the described 

 specimens resemble P. lenticularis Ulrich but cannot be assigned to this species, 

 which has larger and fewer mesopores than the Spechts Ferry material. 



Prasopora simulatrix orientalis is rare in the Spechts Ferry as the collections 

 contain only three specimens from which five thin sections were prepared. 



Distribution. — Localities 4, 6 . 



Types. — Hypotypes, Illinois State Geological Survey, 12P1, 12P15, 12P21. 



Family HETEROTRYIDAE Ulrich, 1890 



Genus DEKAYELLA Ulrich, 1882 



Type species: Dekayella obscura Ulrich 



DEKAYELLA PRAENUNTIA ECHINATA Ulrich 



Plate 3, figures 1-6 



Dekayella praenuntia var. echinata Ulrich, 1895, Geol. Minnesota, 

 v. 3, pt. 1, p. 271, pi. XXIII, figs. 32-38; Caley, 1936, 

 Geol. Survey Canada Mem. 202, pt. II, p. 73, pi. 3, fig. 9, 

 pi. 5, figs. 4-6; Loeblich, 1942, Jour. Paleontology, v. 16, 

 no. A, p. 426, pi. 63, figs. 12-14; Fritz, 1957, Geol. Survey 

 Canada Bull. 42, p. 14, pi. VI, figs. 1, 2. 

 External features. — Zoarium ramose, the largest fragment 31 mm long, 12 

 mm in greatest diameter, and 20 mm wide in region where two branches originate. 

 Monticules rarely observed on weathered surface, very slightly elevated, and 

 composed of zooecia somewhat above average in size surrounding an aggregation 

 of mesopores or of zooecia somewhat larger than ordinary; monticules spaced about 

 3 mm apart, measuring from center to center. 



Tangential section. — Zooecia sharply angular to subangular and having 

 amalgamate walls usually ranging in thickness from slightly less than 0.01 to 



