SPECHTS FERRY BRYOZOAN FAUNA 19 



0.02 mm but very rarely exceeding 0.03 mm thick; typically (31 of 50 measurements) 

 eight entire zooecia and portion of a ninth in 2 mm, measuring parallel to length 

 of zoarium; much less commonly (10 of 50 measurements) seven entire zooecia and 

 part of eighth or (nine of 50 measurements) nine entire zooecia and portion of a 

 tenth in this distance. Mesopores angular to subround, generally ranging in size 

 from one-fifth to nearly one-half the size of a typical zooecium, sporadically dis- 

 tributed, commonly two or three per zooecium but probably averaging about one or 

 less. Acanthopores generally at junction angles of adjoining zooecia, of two dis- 

 tinct sizes with very few of intermediate size; larger acanthopores inflecting, as 

 much as 0.10 mm in diameter but averaging about 0.06 mm, usually about three 

 times the size of the smaller acanthopores and probably at least four times as 

 abundant as the smaller; acanthopores of both sizes irregularly distributed, as 

 many as two or three per zooecium or absent or very rare in local areas, and hav- 

 ing thick nearly opaque walls of concentrically fibrous material surrounding a 

 hollow center. Local areas, approximately 1.5 mm in diameter, composed of small 

 angular tubes flanked by zooecia above average in size or of zooecia larger than 

 ordinary, represent monticules . 



Longitudinal section. — Zooecia erect in axis and bending gradually to 

 meet zoarial surface at right angles. In axis, zooecial walls thin, loosely flex- 

 uous, becoming slightly thicker where zooecia bend somewhat more abruptly to- 

 ward zoarial surface. Laminae of zooecial walls moderately to broadly convex 

 outward; where moderately convex, dark, poorly defined divisional line developed 

 in wall between zooecia; wall laminae obscurely continuous into diaphragms. In 

 axial region, diaphragms variably spaced, from two to five zooecial diameters 

 apart in some zooecia and virtually absent in others; diaphragms in ill-defined 

 mature zone average slightly more than half a zooecial diameter apart. Mesopores 

 not commonly observed, confined to mature zone, and having somewhat more closely 

 spaced diaphragms than the zooecia. 



Remarks. — Dekayella praenuntia echinata is characterized by the sporadic 

 distribution of mesopores and acanthopores; both structures are locally sparse or 

 lacking, but in other parts of the zoarium may be moderately abundant. This species 

 is represented in the Spechts Ferry collections by five specimens, from which nine 

 thin sections were prepared. 



Distribution. — Localities 1, 4, 6, 8, 9. 



Types.— Hypotypes, Illinois State Geological Survey, 12P92, 12P121, 

 12P148, 12P154, 12P162. 



DEKAYELLA sp. 



Plate 6, figures 1-3 



External features. — Not adequately observed because specimen was largely 

 embedded in shale matrix. Zoarium apparently irregularly ramose or bulbous, 26 mm 

 long and 10 mm in maximum diameter. 



Tangential section. — Zooecia sharply angular, less commonly subangular, 

 and generally having thin walls; locally zooecial walls of moderate thickness 

 (0.02 mm) and amalgamate; most commonly (five often measurements) seven entire 

 zooecia and part of eighth in 2 mm, and less commonly (three of ten measurements) 

 eight complete zooecia and portion of ninth or (two of ten measurements) nine entire 

 zooecia and part of tenth in this distance. Acanthopores exceptionally abundant, 

 usually three to five but as many as seven associated with each zooecium, of two 

 distinct sizes, and located at junction angles of adjoining zooecia; the larger 



