6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I39 



V-shaped pattern that has extremely long limbs trending nearly 

 parallel to the boundary and curving very slightly just before the 

 boundary is intersected. Laminae of walls of zooecia and adjacent 

 mesopores are more broadly curved approaching the median boundary 

 and form a broad U-shaped pattern having limbs of varying lengths. 

 Acanthopores are common in the zooecial walls. 



Discussion. — Based on an examination of thin sections of primary 

 types of species previously assigned to Trematopora now in the U. S. 

 National Museum collections, the following species are considered cor- 

 rectly assigned to the genus : 



T. halli Ulrich 1883, Niagaran group, Waldron, Ind. 



T. whitfieldi Ulrich 1883, Niagaran group, Waldron, Ind. 



The holotype section of T. spiculata Miller 1877, Niagaran group, 

 Waldron, Ind., is not adequate to determine generic affinities. This 

 species is retained in the genus until a more detailed study of addi- 

 tional material can be made. 



The following species originally placed in Trematopora do not 

 satisfy the generic definition proposed here and are not considered to 

 belong to the genus. Their proper generic assignments must await 

 restudy of both the species themselves and the available genera. 



calloporoides Ulrich 1890, Cincinnati group, Alexander County, 111. 



cystata Bassler 191 1, Kuckers shale (C2), Reval, Esthonia. This 

 species is the type of Aostipora Vinassa 1920). 



debilis Ulrich 1890, Girardeau limestone, Alexander County, 111. 



kukersiana Bassler 191 1, Kuckers shale (C2), Reval, Esthonia. 



primigenia Ulrich 1886, Decorah shale, Minneapolis, Minn. 



primigenia var. ornata Ulrich 1886, Decorah shale, Minneapolis, 

 Minn. 



None of the Ordovician species investigated displayed the two 

 regions of the exozone or pores in the mesopore diaphragms. Thus, 

 the genus is limited presently to the Middle Silurian. 



A close taxonomic relationship seems to exist between Trematopora 

 and some or all of the Silurian and Devonian species that have been 

 placed in the genus Leioclema Ulrich. These species of Leioclema 

 are largely incrusting and possess many of the morphologic characters 

 now defining Trematopora. In general they have elliptical zooecia 

 with few thin diaphragms, abundant mesopores with closely spaced 

 thicker diaphragms and an irregularly discontinuous inner region of 

 the exozone containing beaded mesopores. Pores in the diaphragms 

 of the mesopores are rare but do definitely occur in the following 

 species. 



