SPECHTS FERRY BRYOZOAN FAUNA 13 



HOMOTRYPA DICKEYVILLENSIS Perry, n. sp. 

 Plate 2, figures 5-9 



External features. — Zoarial fragment ramose, 14 mm wide and 32 mm long, 

 and showing proximal part of one bifurcation; neither monticules nor maculae ob- 

 served on weathered zoarial surface. 



Tangential section. — Zooecia typically angular, rarely subangular, and 

 having amalgamate walls that are usually 0.02 or 0.03 mm thick; generally (12 of 

 20 measurements) eight entire zooecia and portion of ninth in 2 mm, measuring 

 parallel to length of zoarium; less commonly (six of 20 measurements) seven entire 

 zooecia and part of eighth in this distance; and rarely (one of 20 measurements) 

 seven or (one of 20 measurements) nine entire zooecia in 2 mm. Cystiphragms 

 prominent, observed in nearly all zooecia, and typically enclosing about one-sixth 

 of the apertural area of each zooecium. Acanthopores generally sparse, moderately 

 abundant in local areas, small, commonly at junction angles of adjoining zooecia, 

 rarely mildly inflecting, and with thick,dark, opaque walls surrounding small hollow 

 center. Where relatively abundant, generally one, less commonly two, acantho- 

 pores associated with each zooecium; where rare, one associated with ten or more 

 zooecia. Two areas consisting of zooecia generally lacking cystiphragms and 

 usually above average size probably represent monticules. Mesopores probably 

 lacking, but small subangular or subround zooecia not uncommon. 



Longitudinal section. — Zooecia thin-walled and locally crenulated or flex- 

 uous in mature and submature regions, becoming thicker walled at base of well 

 defined mature zone. Locally zooecial walls appear integrate, showing centrally 

 located somewhat undulatory dark line; shape or orientation of laminae in zooecial 

 wall not discernible. Zooecia bend gradually to zoarial surface, the zooecial 

 curvature increasing somewhat at base of mature region. Diaphragms very sparse 

 in axis, two to four zooecial diameters apart in poorly defined submature zone, 

 and one-half zooecial diameter apart, or less, in mature zone where each zooecium 

 usually contains from seven to thirteen diaphragms. Cystiphragms prominent, com- 

 monly occupying one-half the width of each zooecium, usually in one series but 

 rarely extending from both sides of the zooecium; earliest formed cystiphragms at 

 base of mature region; material forming cystiphragms obscurely continuous with 

 zooecial wall material. Mesopores not observed. 



Remarks. — This species is characterized by its moderately thick zooecial 

 walls and the sharply defined base of the mature zone, which is marked by thicken- 

 ing of zooecial walls, the abrupt appearance of well developed cystiphragms, and 

 the closer spacing of the diaphragms. In tangential sections, cystiphragms are 

 conspicuous structures in virtually all zooecia, except in larger zooecia forming 

 the monticules in which cystiphragms are lacking or poorly developed. Zooecial 

 walls in the axial and submature regions are commonly crenulated or wrinkled, as 

 may be observed in many species of Homotrypa. 



Homotrypa dickeyvillensis differs from all Bromide (late Blackriveran) 

 species of Homotrypa described by Loeblich (1942, p. 420-422) in having dia- 

 phragms very sparsely developed in the axial region; diaphragms in Bromide species 

 recognized by Loeblich, in contrast, are spaced three zooecial diameters apart, 

 or less, in the axial region. H. dickeyvillensis does not compare closely with 

 any Cincinnatian species of Homotrypa described by Bassler (1903, p. 565-591) 

 or by Cumings and Galloway (1912, p. 429-432) nor does this species resemble 

 forms described by Fritz (1957, p. 22, 23) from the Ottawa Formation (Black River- 

 Trenton) of the Ottawa-St . Lawrence Lowland . 



