12 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 326 



12P97, 12P102, 12P103, 12P104, 12P105, 12P109, 12P110, 12P111, 12P117, 12P118, 

 12P119, 12P120, 12P123, 12P126, 12P127, 12P128, 12P130, 12P131, 12P134, 12P137, 

 12P138, 12P140, 12P142, 12P144, 12P145, 12P150, 12P151, 12P152, 12P153, 

 12P155, 12P157, 12P158, 12P159, 12P163, 12P164, 12P165, 12P167, 12P171, 12P173, 

 12P174, 12P175, 12P176, 12P177, 12P179, 12P180, 12P183, 12P186, 12P188, 

 12P189, 12P192, 12P193, 12P194, 12P196, 12P197, 12P199. 



HOMOTRYPA PAUPERATA Perry, n. sp. 

 Plate 2, figures 1-4 



External features. — Zoarium ramose, solid, elliptical in cross section, 

 the largest incomplete specimen 12 mm in maximum diameter and 10 mm in minimum 

 diameter and 39 mm long. Maculae, usually spaced 3.0 to 4.5 mm apart measur- 

 ing from center to center, composed mainly of about eight zooecia above average 

 in size. 



Tangential section. — Zooecia angular or subangular, very thick-walled, 

 and having broadly ovate to subpolygonal apertures; most commonly (13 of 25 

 measurements) nine entire zooecia and part of tenth in 2 mm, measuring parallel 

 to length of zoarium; less commonly (nine of 25 measurements) ten entire zooecia 

 and portion of eleventh in this distance; average maximum apertural diameter 

 (based on 25 measurements) of zooecia 0.16 mm, ranging from 0.14 to 0.19 mm; 

 average interapertural zooecial wall thickness (based on 20 measurements) nearly 

 0.07 mm, ranging from 0.04 to 0.10 mm. Zooecial wall composed of a broad, dark- 

 colored band of fibrous and granular tissue flanked on either side by lighter colored 

 laminated material, the laminae parallel to zooecial apertures. Maculae formed 

 entirely of zooecia above average in size or of larger zooecia and a small number, 

 usually one to four, of intercalated mesopores. Acanthopores not observed. Meso- 

 pores uncommon, thick-walled, and subpolygonal. 



Longitudinal section. — Zooecia erect, thin-walled, straight or slightly 

 flexuous in axis, thickening abruptly at base of mature zone where they bend sharp- 

 ly to zoarial surface. Zooecial wall in mature zone commonly but not invariably 

 showing dark-colored divisional line between zooecia; wall material of fine laminae 

 moderately to broadly convex outward. Diaphragms lacking in axis; ten to fifteen 

 per zooecium in broad mature zone where diaphragm spacing approximates half 

 zooecial diameter. Cystiphragms not present in all zooecia, generally terminating 

 proximally at diaphragm and arching distally to unite with zooecial wall. Mesopores 

 probably not observed. Acanthopores lacking. 



Retnarks. — Homotrypa pauperata and H. exilis Ulrich are closely allied 

 species, as both have thick zooecial walls and presumably lack acanthopores. 

 Distinguishing characteristics of these species are: (1) cystiphragms are more 

 abundant in H. exilis; (2) average zooecial wall thickness is greater in H. pauper- 

 ata; (3) microstructure of the zooecial walls, particularly where observed in tangen- 

 tial section, differs in these species; (4) H. pauperata has fewer mesopores; and 

 (5) H. pauperata has smaller zooecia and thus displays more of these structures 

 in a 2-mm distance than H. exilis . 



The specific name pauperata means "impoverished" and alludes to the rather 

 sparse development of cystiphragms. The species is represented in the Spechts 

 Ferry collections by two specimens from which four tangential and two longitudinal 

 sections were prepared. 



Distribution. — Localities 2, 6. 



Types. — Illinois State Geological Survey; holotype 12P129, paratype 12P241. 



