NO. 6 BRYOZOAN GENUS TREMATOPORA — BOARDMAN 5 



Evidence concerning the position of the soft parts in the outer 

 region of the mesopore is inadequate. Configurations of the laminae 

 give no indications of deposition behind the distalmost diaphragm. 

 The common occurrence of single, centrally located pores that either 

 partly or completely penetrate the thick outer diaphragms suggest some 

 activity within outer chambers. The majority of these central pores 

 appear to have been cut through the laminae of the diaphragms. Their 

 termination within outermost diaphragms suggests that activity within 

 the outermost chambers might have been choked off by the growth of 

 the thickened diaphragms. 



SYSTEMATIC DESCRIPTION 

 Genus TREMATOPORA Hall, 1851 



185 1. Trematopora Hall, Amer. Journ. Sci. and Arts, ser. 2, vol. II, p. 400. 



1852. Trematopora Hall, Paleontology of New York, vol. 2, p. 149. 



1881. Trematopora Hall, Nicholson, Genus Monticulipora, pp. 232-234. 



1882. Trematopora Hall, Ulrich, Journ. Cincinnati Soc. Nat. Hist., vol. 5, p. 



241. 



1883. Trematopora Hall, Ulrich, Journ. Cincinnati Soc. Nat Hist., vol. 6, p. 



257. 

 1887. Trematopora Hall, Hall and Simpson, Paleontology of New York, vol. 



6, p. xiv. 

 1893. Trematopora Hall, Ulrich, Geol. Minnesota, vol. 3, pt. 1, p. 308. 

 191 1. Trematopora Hall, Bassler, U. S. Nat. Mus. Bull. 77, pp. 267, 268. 

 1882. [non] Trematopora Hall, Ulrich, Journ. Cincinnati Soc. Nat. Hist., vol. 



5, P- 153. 



Type species. — Trematopora tuberculosa Hall, 1852. 



Emended definition. — Zoaria are ramose, conspecific overgrowth is 

 common, and monticules range from level to tuberculated. Externally, 

 zooecia are elliptical to subcircular in cross section and walls are 

 slightly elevated above intervening mesopores. Mesopores form 

 shallow, subpolygonal depressions between zooecia. 



The exozone is divided into an inner thin-walled region containing 

 the earliest chambers of the mesopores and an outer thick- walled 

 region. In the inner region, both mesopores and zooecia are polygonal 

 to subpolygonal in cross section and mesopores are beaded and contain 

 diaphragms with single central pores. In the outer region of the 

 exozone, zooecia become elliptical to subcircular in cross section and 

 the mesopores contain thickened diaphragms and are not beaded. 

 Diaphragms are thin and few in zooecia. 



In the outer region of the exozone, walls of adjacent zooecia are 

 divided by sharply defined zooecial boundaries, as seen in longitudinal 

 sections. Laminae on either side of a boundary converge to form a 



