26 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 326 



Longitudinal section. — Zooecia erect, thin-walled in axis, bending grad- 

 ually to meet zoarial surface, the curvature increasing somewhat at base of mature 

 zone where diaphragm spacing markedly diminishes and zooecial wall thickness 

 increases. Diaphragms in axis usually spaced from somewhat over one to about 

 five zooecial diameters apart and in mature region generally spaced from slightly 

 less than one-half to nearly one zooecial diameter apart. Mesopores closely tabu- 

 late and not observed below base of mature zone. Acanthopores locally conspicuous 

 in mature zone but generally observed only in a short segment of zooecial wall . 



Remarks. — The Spechts Ferry collection includes only one specimen of this 

 distinctive form from which two longitudinal and two tangential sections were pre- 

 pared. Unfortunately, the specimen has undergone silicification to a considerable 

 depth within the mature region; this form of preservation has largely obliterated 

 details of wall structure, but locally and obscurely the walls appear integrate in 

 tangential section. 



Distribution. — Locality 9. 



Type. — Hypotype, Illinois State Geological Survey, 12P219. 



BATOSTOMA WINCHELLI (Ulrich) 



Plate 6, figures 4-11 



Amplexoporawinchelli Ulrich, 1886, 14th Ann. Rept., Geol . Nat. Hist. 



Survey Minnesota, p. 91. 

 Batostorna winchelh Ulrich, 1895, Geol. Minnesota, v. 3, p. 295, 

 pi. 26, figs. 33, 34, 36, 37, pi. 27, figs. 1-6; Bassler, 1911, 

 U. S. Nat. Mus. Bull. 77, p. 278, 279, fig. 166; Wilson & Mather, 

 1916, Ontario Bur. Mines, v. 25, pt . 3, p. 49, 55; Wilson, 

 1921, Geol. Survey Canada Bull . 33, Geol. Ser. 40, pi. II, 

 figs. 7, 8; Loeblich, 1942, Jour. Paleontology, v. 16, no. 4, 

 p. 432, pi. 64, figs. 8-10; Wilson, 1949, Tennessee Div. 

 Geol. Bull. 56, pi. 13, fig. 11; Fritz, 1957, Geol. Survey 

 Canada Bull. 42, pi. IV, figs. 1-3. 

 External features. — Zoarium ramose, the fragments ranging in length from 

 10 to 31 mm and in width from 3.5 to 9 mm and commonly showing one bifurcation. 

 Zooecia thick-walled, angular to subangular; acanthopores locally abundant, 

 particularly where zooecial walls are somewhat thinner. Zoarial surface smooth 

 and showing sparse irregularly distributed maculae composed of several zooecia 

 above average in size or of large and small tubes. 



Tangential section. — Zooecia angular to subangular and usually having 

 broadly ovate or subangular apertures; most commonly seven entire zooecia and 

 part of eighth in 2 mm, measuring parallel to length of zoarium. Zooecial walls 

 most commonly integrate but locally amalgamate, the wall thickness ranging from 

 0.02 to 0.16 mm but usually from 0.04 to 0.06 mm. Acanthopores generally at 

 junction points of adjoining zooecia, usually small but commonly of medium size, 

 rarely inflecting and, where abundant, two to six, typically three or four, acantho- 

 pores associated with each zooecium; where sparse, two to four occurring with ten 

 zooecia; many acanthopores lacking hollow centers and composed of concentrically 

 arranged black fibers. Mesopores absent or, when rare, small. Maculae composed 

 of six to eight zooecia about one-quarter larger than those of intermacular areas 

 or of large and small tubes. 



Longitudinal section. — Zooecia erect in axis, bending gradually to inter- 

 sect zoarial surface at right angles. Diaphragms in axis usually one to eight, 



