NO. 6 



BRYOZOAN GENUS TREMATOPORA — BOARDMAN 



found in the walls of zooecia and mesopores in the outer region of the 

 exozone, and in the inner region in some of the thicker mesopore walls 

 and in the vicinity of central pores in the mesopore diaphragms 



(fig- i). 



Assuming that secreting tissue was oriented parallel to the laminae, 

 transversely laminated structure indicates that the tissue must have 

 been wrapped around the growing edges of walls and diaphragms 



Inner Region 

 of Exozone 



Outer Region 

 >■-< of Exozone > 



MESOPORE -*- 



Fig. i. — Idealized diagram of T. tuberculosa in longitudinal view illustrating 

 the variety of laminated structures commonly occurring in the species. Two 

 mesopores and an intervening zooecium are shown in profile. Few central pores 

 of the mesopore diaphragms are intersected in a longitudinal section. 



on both sides of the median lines. Thus, transversely laminated struc- 

 ture presumably indicates deposition from both sides of a wall or 

 diaphragm. 



Such interpretations applied to the skeletal laminae of T. tuberculosa 

 and correlated with other morphologic characteristics of the species 

 suggest that the exozone is divisible into two parts, an inner and an 

 outer region (fig. i) based on fundamentally different modes of 

 growth of the mesopores. The physiologic significance of the two 

 modes of growth is a matter for speculation. The taxonomic signifi- 

 cance of these characters must await comparable studies in related 

 genera. 



