RUB-ORDER B 



TRKl'OSTOMATA 



275 



Callopora, Hall (emend. Ulrich), (Fig. 456). Zoaria usually ramose and bushy, the 

 branches often anastomosing. Apertures closed in the perfect state by perforated, 

 often ornamented, covers, which are It-It behind, as growth proceeds, to form floors 

 {diaphragms) of succeeding layers. Zocecial tubes of two sizes in the axial region, the 

 larger ones with six to eight sides, the smaller set four- or five-sided. Ordovician and* 

 Silurian, 



Diplotrypa, Nich. emend. Ulrich (Dianulites, Zittel non Dybowski), (Fig. 457). 

 Zoaria discoid, globular, or irregularly massive, generally free. Zocucial tubes com- 

 paratively large, prismatic, with horizontal diaphragms. Mesopores few to numerous, 

 varying in size. Ordovician. 



Monotrypa, Nich. (Dianulites, Dyb. p.p. ; ftychonema, Hall), (Fig. 458). Dis- 

 tinguished from the preceding by the absence of mesopores and fewer diaphragms. 

 Ordovician to Devonian. 



Family 4. Trematoporidae. Ulrich. 



Zoaria ramose or encrusting. Zo&cial tubes irregular in the axial region, their 

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



FIG. 459. 



Tangential sections of Batostoma from the Lower Trenton of Minnesota. A, B. fertile, Ulr. 

 var. circulare, M/j. C, B. Winchdli, var. spinulosum, Ulr., 38/ : (after Ulrich). 



i. B Same 



thickened in the mature region, lines of contact distinct, 

 usually of large size, their apertures 

 closed. Acanthopores more or less 

 abundant. Ordovician. 



Mesopores generally abundant, 



This family is principally distinguished 

 m the Cailovoridae by the presence of 



from the Calloporidae 

 acanthopores and closed mesopores. 



Batostoma, Ulrich (Fig. 459). 

 Branches irregular, springing from a 

 large basal expansion. Zooecial walls 

 of varying thickness, in contact only 

 at limited points, and of two sizes in 

 the axial region. Diaphragms strong, 

 horizontal, complete. Species numer- 

 ous and mostly very abundant. 



Hemiphragma, Ulrich (Fig. 460). 

 part of tubes incomplete. 



Trematopora, Hall (emend. Ulrich) ; Stromatotrypa, Ulrich. 



Fio. 460. 



Hemiphragma irrasum, Ulr. Lower Trenton ; Minnesota. 

 A, Vertical section, 7/,. B, Tangential, w/j (after Ulrich). 



Like Batostoma, but diaphragms in peripheral 



