338 



MOLLUSCOIDEA— BRYOZOA 



PHYLUM V 



Family 7. Trematoporidae Uliicli. 



Zoaria ramose or encrusting. Zooecial tuhes irregular in the axial region, their 

 proximal ends with diaphragms, and usually constricted ivhere the latter occiir ; walls 



A B 





Fig. 492. 



Tangential sections ot BatoKtovm from the Black River Group of Minnesota. A, B. fertile Ulr., '>'i/j. 

 B, Same, var. circulare, l-*/j. C, B. tinnchelli var. spinulosam Ulr., 38/j (after Ulricli). 



thickened in the mature region, lines of contact distinct. Mesopores generally abundant, 

 usually of large size, their apertures closed. Acanthopores more or less abundant. 



This family is principally distinguished from the Halloporidae by the presence of acantho- 

 pores and closed mesopores. The Trematoporidae, moreover, have a general looseness and 

 obscurity of structure quite unlike that of any other Trepostomata. 



Batostoma Ulr. (Fig. 

 A 



492). 



B 





Hemiphragma irrasum Ulr. Lower Trenton ; Minnesota, 

 A, Vertical section, T/j. B, Tangential, "/i (after Ulricli). 



Branches irregular, springiirg from a large basal 

 expansion. Zooecial walls of varying 

 thickness, in contact only at limited 

 IJoints, and of two sizes in the axial 

 region. Diaphragms strong, horizon- 

 tal, complete. Species numerous and 

 mostly very abundant. Ordovician 

 and Silurian. 



Hemiphragma Ulr. (Fig. 493). 

 Like Batostoma, but diaj^hragms in 

 peripheral part of tubes incomijlete. 

 Ordovician and Silurian. 



Diplotrypa Nich., emend. Ulr. 

 (Fig. 494). Zoaria massive, generally 

 free. Zooecial tubes comparatively 



494. 



Diplotrypa westoni Ulr. Richmond Group ; Manitoba. 

 Tangenti.al and vertical sections, i-^/j (after Ulricli). 



Fi(i. 495. 



Mnnritryprt wagiia Ulr. Lower Trenton ; Illinois. 

 Transverse and vertical sections, l/i (after Ulricli). 



