338 



MOLLUSCOIDEA— BRYOZOA 



PHYLUM V 



Family 7. Trematoporidae Ulrich. 



Zoaria ramose or encrusting. Zocecial tuhes irregulär in the axial region, their 

 proximal ends with diaphragms, and usually constricted where the latter occur ; walls 



Fio. 492. 



Tangential sections of Batostoma from the Black River Group of Minnesota, A, B. fcrtile Ulr., H/j. 

 B, Same, var. circulare, l-J/j. C, B. tvinchelli var. spinulosum Ulr., 38/^ (after Ulrich). 



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

 usually of large size, their apertures closed. Äcanthopores more or less ahundant. 



This faraily is principally distinguislied from the Halloporidae by the presence of äcantho- 

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

 obscurity of structure quite unlike that of any otlier Trepostomata. 



Batostoma 



492). 



Branches. irregulär, springing from a large basal 

 expansion. Zooocial walls of varying 

 thickness, in contact only at limited 

 points, 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). 

 but diaphragms in 

 tubes incomplete. 

 Ordovician and Silurian. 



Diplotrypa Nich., emend. Ulr. 



Hemiphragma irrasum mr. Lower Trenton ; Minnesota. /Tri:„ ACkA\ ^r^^r.\n w,or,.,;,.^ ^^ ^^.,n,r 



A, Vertical section, 1^. B, Tangential, H/^ (after Ulrich). (^ ^^' ^^V' /f^Oaria massive, generally 



free. Zooccial tubes comparatively 



AV* ^^~^^^ ^.^«Ä^W'" ' ■'-'ik^ Batostoma, bi 

 W^ kit^'M"\C^^ peripheral part of 



Fig. 493. 



Fig. 494. 



Diplotrypa westoni Ulr. Richmond Group ; Manitoba. 

 Tangential and vertical sections, i4/j (after Ulrich). 



Fig. 495. 



Monotrypa magna Ulr. Lower Trenton ; Illinois, 

 Transverse and ^'ertical sections, 7/j (after Ulrich). 



