NO. 6 BRYOZOAN GENUS TREMATOPORA — BOARDMAN II 



pearance is caused by extreme inflection of zooecial walls by adjacent 

 acanthopores and mural spines. Acanthopores are large, laminated, 

 possess well-defined central tubes, and are generally located at points 

 of closest proximity of adjacent zooecia. Mural spines appear to begin 

 outside the broad band of striated-appearing tissue lining each 

 zooecium and project inwardly toward the zooecial void, strongly in- 

 flecting the laminated tissue but not breaking through to the void. 

 Mesopores are numerous, subpolygonal to subcircular. In very shallow 

 sections that pass through the outermost and thickest diaphragms, 

 mesopore boundaries are concealed and interspaces between zooecia 

 appear solid. Many of these solid interspaces do not show the smaller 

 central pores that are the rule in sections that pass through earlier 

 parts of the outer region. 



In deeper tangential sections that pass through the inner region of 

 the exozone, zooecia are polygonal to subpolygonal and approximately 

 equidimensional. Mesopores are also polygonal to subpolygonal and 

 have fewer sides than the zooecia, merely appearing to fill the spaces 

 between zooecia. Pores in mesopore diaphragms here are several 

 times larger in diameter than those in the outer region. Acanthopores 

 are considerably smaller in diameter than they are in the outer region. 



QUANTITATIVE DATA 



The following tables are based on sections of two fragments from 

 the lectotype, three fragments from the two paratype zoaria, and 49 

 fragments from 33 topotype zoaria. Sections from 55 zoaria of 

 Trematopora tuberculosa were examined. All measurements are in 

 millimeters. The axial ratio is the ratio of the diameter of the endo- 

 zone to the corresponding branch diameter. 



Table i. — General measurements 



Lectotype AMNH Paratypes and 



1747 topotypes 



Frag. A. Frag. B. 



Diameter of zoarium 6.5 4.9 



Width of endozone 5.3 3.3 



No. zooecia in 2 mm. (longitudinal 



direction) 5i 6£ 6 8 



Average major axis of zooecial void 



per fragment 0.14 0.15 0.14 0.22 



Average minor axis of zooecial void 



per fragment 0.12 0.12 



Acanthopores per zooecium 0.73 0.63 



Mesopores per zooecium 1.6 — 



