SPECHTS FERRY BRYOZOAN FAUNA 23 



developed and irregularly distributed, typically at junction angles of adjoining 

 zooecia, commonly none to three, very rarely as many as six, associated with ten 

 zooecia; acanthopore wall of dark, nearly opaque, concentrically laminated tissue 

 differentiated sharply from zooecial wall material. Mesopores subovate to sub- 

 angular, few, ten intermonticular zooecia commonly lacking an associated meso- 

 pore. Monticules consisting of clustered mesopores flanked by zooecia above 

 average in size . 



Longitudinal section. — Zooecial walls in axis thin, straight or mildly flex- 

 uous, and thickening gradually toward zoarial surface; zooecial walls in mature 

 zone of fine laminae, moderately to broadly convex outward, and continuous into 

 diaphragms. Zooecia erect in axis, curving gradually outward, and meeting zoarial 

 surface at right angles. Diaphragms generally spaced one-half zooecial diameter 

 apart in mature zone and from one to three zooecial diameters apart in submature 

 region; diaphragms of variable abundance in axis, virtually lacking in a few zooecia, 

 but customarily spaced from three to seven zooecial diameters apart; locally dia- 

 phragms arched, convex outward, and uniting with adjacent proximal diaphragm. 

 Mesopores rare, containing closely spaced diaphragms, and not observed below 

 mature region. 



Remarks. — Heterotrypa pauca is represented in the Spechts Ferry collections 

 by 20 sectioned specimens. This species may be identified by its thick amalga- 

 mate walls, its sparse and irregularly distributed acanthopores, and its few meso- 

 pores. In tangential sections of some specimens, acanthopores are so exception- 

 ally rare that only two or three of these structures are observed in an entire section 

 that may include several hundred zooecia. A few specimens are assigned to this 

 species although acanthopores are not seen in their tangential sections; such 

 specimens, however, are similar structurally in all other respects to forms that 

 show rarely developed acanthopores. H. pauca has fewer acanthopores than any 

 other described species of Heterotrypa of Ordovician age. The number of zooecia 



EXPLANATION OF PLATE 6 



Figures 2-5 and 8 are X60; all others are X20. 



Specimen number and collecting locality are shown in parentheses follow- 

 ing explanation of each figure; for example, (12P87, 5) refers to specimen 12P87 

 obtained from collecting locality 5. Structures in photographs are not retouched. 



Figure 



1-3 Dekayella sp. 1. Tangential section (12P87, 5). 2. Tangential sec- 



tion showing abundant acanthopores of two distinct sizes (12P87, 5). 

 3. Small part of zooecial wall in mature zone showing acanthopores 

 and zooecial wall structure (12P87, 5). 



4.-11 Batostoma winchclli (Ulrich) . 4. Longitudinal section showing integrate 



zooecial wall of mature zone (12P156, 8). 5. Longitudinal section 

 displaying cingulum (12P198, 6). 6. Tangential section showing 

 distinctly integrate zooecial walls (12P198, 6). 7. Longitudinal 

 section (12P198, 6). 8. Tangential section showing integrate 

 zooecial walls and mildly inflecting acanthopores (12P218, 10). 9. 

 Longitudinal section (12P67, 6). 10. Tangential section showing 

 development of acanthopores characteristic of species (12P67, 6). 

 11 . Tangential section displaying integrate zooecial walls and 

 inconspicuous acanthopores (12P191, 6). 



