BRYOZOA—TREPOSTOMATA. 129 



40. H. obliqua Ulrich. Ordovicic. 

 Flattened branches with well-developed monticules as in Monti- 



culipora, from which it is readily distinguished by the larger cells 

 of the monticules. 



Lorraine of Cincinnati region. 



41. H. curvata Ulrich. Ordovicic. 

 Differs from preceding in absence of monticules, and occurrence 



of stellar maculae of minute cells, but appearing smooth, and sur- 

 rounded by larger cells than average. 

 Lorraine of the Cincinnati region. 



42. H. flabellaris Ulrich. Ordovicic. 

 Growth fan-shaped, surface with obscure maculae with centers 



about 4 mm. apart; walls of tubes very thin, appearing flexuous 

 or crenulated in section, with few remote diaphragms in zocecia, 

 but many in mesopores. 



Lorraine and Richmond of Illinois, Ohio, Indiana, Kentucky 

 and Tennessee. Common. 



43. H. minnesotensis Ulrich. Ordovicic. 

 Subcylindrical branches from 5 to 15 mm. in. diameter, gener- 

 ally dividing dichotomously ; clusters of larger cells conspicuous 

 in one variety, raised on monticules, about 25 mm. between cen- 

 ters ; true mesopores wanting, acanthopores exceedingly small 

 and few; apertures oblique. 



Stones River and Black River of Minnesota, Iowa, Kentucky, 

 and Tennessee. 



XXIX. Prasopora Nicholson and Etheridge. 



Massy, usually free, with wrinkled |epitheca on under side; 

 zocecia prismatic or cylindrical, thin-walled, with cystiphragms, 

 and generally surrounded by angular mesopores with crowded 

 diaphragms ; acanthopores rarely numerous or strong. Ordovicic. 



44. P. simulatrix Ulrich. (Fig. 186, d.) Ordovicic. 

 Discoidal to hemispheric or subconic, base concave; clusters of 



larger cells with more numerous mesopores at intervals of about 

 4 mm., sometimes on monticules ; an average of 1 1 cells in 

 3 mm. 



Black River and Trenton of Kentucky, Tennessee, Wisconsin, 

 and Minnesota. 



