20 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 326 



acanthopores conspicuously inflecting zooecial apertures, about twice as abundant 

 as the smaller set, commonly 0.05 mm in diameter, and having thick dark walls of 

 concentrically fibrous material surrounding hollow center. Small tubes (presumably 

 mesopores) nearly lacking in some areas of section but elsewhere moderately abun- 

 dant. Evidence of either monticules or maculae not observed. 



Remarks. — Three longitudinal sections were prepared, but none can be in- 

 terpreted satisfactorily because of poor orientation, which precludes specific iden- 

 tification. The specimen is assigned to the genus Dekayella as it has acanthopores 

 of two distinct sizes. This form clearly differs from D. praenuntia echinata Ulrich 

 in having considerably more numerous acanthopores and thinner zooecial walls. 



Distribution. — Locality 5 . 



Described specimen .— Illinois State Geological Survey, 12P87. 



Genus HETEROTRYPA Nicholson, 1879 



Type species: Heterotrypa frondosa (d'Orbigny) 



HETEROTRYPA PAUCA Perry, n. sp. 



Plate 4, figures 1-8 



External features. — Zoarium ramose, the fragments as much as 16 mm in 

 diameter, 44 mm in length, and commonly showing areas of bifurcation. Surface 

 smooth or showing low monticules composed of zooecia above average in size and 

 intercalated mesopores; monticules spaced 3.0 to 4.0 mm apart, measuring from 

 center to center. Where smooth, zoarial surface with clusters of zooecia of above 

 average size and associated mesopores. 



Tangential section. — Zooecia angular to subangular, generally five- or 

 six-sided, and having amalgamate walls that commonly are 0.02 or 0.03 mm thick; 

 central portion of zooecial wall composed of light-colored laminated material that 

 is flanked on either side by thin zone of dark-colored laminated tissue; typically 

 (110 of 200 measurements) eight entire zooecia and portion of ninth in 2 mm, meas- 

 uring parallel to length of zoarium. Acanthopores small- to medium-sized, sparsely 



EXPLANATION OF PLATE 5 



Figures 3 and 5 are X60; all others are X20. 



Specimen number and collecting locality are shown in parentheses follow- 

 ing explanation of each figure; for example, (12P68, 6) refers to specimen 12P68 

 obtained from collecting locality 6. Structures in photographs are not retouched. 



Figure 



1-3 Monotrypella normalis Perry, n. sp. 1. Tangential section of holotype 



showing macula in upper right of illustration (12P68, 6). 2. Longi- 

 tudinal section (12P68, 6). 3. Small part of transverse (axial) sec- 

 tion showing dark-colored line of demarcation (divisional line) of 

 zooecial wall in mature zone (12P68, 6). 



4-6 Batostoma winchelli spinulosum Ulrich. 4. Tangential section (12P219, 



9) . 5 . Tangential section showing prominent and abundant acantho- 

 pores (12P219, 9). 6. Longitudinal section (12P219, 9). 



7-8 Diplotrypa sp. 7. Tangential section (12P207, 10). 8. Longitudinal 



section showing mesopores (12P207, 10). 



