132 



NORTH AMERICAN INDEX FOSSILS. 



gonal ; mesopores irregular, scattered, sometimes in clusters ; 

 height 2 mm. or more ; width I cm. or less ; thickness I to 4 mm. 

 Hamilton of Iowa and Illinois. 



XXXV. Dekayella Ulrich. 

 Ramose, zocecia with numerous diaphragms, large and small 

 acanthopores, and a variable number of mesopores. Ordovicic. 



53. D. praenuntia Ulrich. (Figs. 188, b, 190, b.) Ordovicic. 



FlG. 188. b, Dekayella^prcBttuntia var. echinata ; e, Bythopora herricki ; f, Erido- 

 trypa mutabilis ; i, Constellaria florida ; j, Batostoma winchelli ; k, B. fertile ; m, 

 Stromatotrypa ovata ; n, Callopora tnultitabulata ; o, Nicholsonella pulchra, broad 

 form. All natural size. For further illustrations see Fig. 190, corresponding letters. 

 (All after Ulrich. ) 



Compressed cylindrical, from 4 to 12 mm. in diameter; no 

 monticules, but inconspicuous clusters of large cells ; few, irregu- 

 larly disposed mesopores and acanthopores. 



Black River of Minnesota. 



54. D. obscura Ulrich. Ordovicic. 

 Small, slender stems, variously branching; monticules obscure. 

 Utica of the Cincinnati region. 



55. D. ulrichi (Nicholson). Ordovicic. 

 Coarse, subcylindricarbranching stems, three or more times the 



diameter of preceding ; low monticules of smaller cells (meso- 



