136 NORTH AMERICAN INDEX FOSSILS. 



65. C. varia Ulrich. (Fig. 190, h.) Ordovicic. 

 Flattened branches with large, irregularly stellate maculae very 



slightly depressed ; zocecial apertures in clusters of from 4 to 10 

 each, slightly or not at all elevated ; apertures subcircular. 

 Trenton of Minnesota, Canada and Tennessee. 



66. C. florida Ulrich. (Fig. 188, i.) Ordovicic. 

 Flattened branches covered with crowded " stars," the rays 



sharp, petaloid and strongly elevated. 



Lorraine of Cincinnati, Ohio, Indiana, Kentucky and Tennessee. 



Common. 



XLII. Nicholsonella Ulrich. 



Laminar expansions, sometimes giving off flattened intertwining 

 branches or fronds ; interzocecial spaces wide, with numerous meso- 

 pores, having thicker and more numerous diaphragms than zocecial 

 tubes, but obliterated with age by filling of secondary calcareous 

 deposit. Ord.-Sil. 



67. N. vaupeli Ulrich. Ordovicic. 

 Flattened, inosculating expansions with evenly distributed, low 



monticules of larger pores than ordinary, with center free from 

 pores. 



Lorraine of Cincinnati region. 



68. N. pulchra Ulrich. (Fig. 188, 0, 190, o' .) Ordovicic. 

 Irregular, flattened branches, monticules faint and often indefi- 

 nite ; interzocecial space papillose. 



Stones River of Tennessee. 



XLIII. Batostoma Ulrich. 

 Irregular branches from large basal expansion; zocecia thin- 

 walled in immature and thick in mature region, ring-like in section, 

 with diaphragms ; mesopores irregular; acanthopores large. Or- 

 dovicic. 



69. B. winchelli Ulrich. (Fig. 188,/, 190,7.) Ordovicic. 

 Subcylindrical or slightly compressed branches 4 to 10. mm. in 



diameter, with rounded or subangular zocecial apertures with ridge- 

 like walls bearing acanthopores, Mesopores few. 

 Black River of Minnesota. 



70. B. fertile Ulrich. (188, k, 190, k.) Ordovicic. 

 Large, of coarse, compressed branches, with round or polygonal 



