134 NORTH AMERICAN INDEX FOSSILS. 



6 1. B. spinulosa (Hall). (Fig. 189.) Siluric. 

 Oval apertures on cylindrical branches with strong spines at 



regular intervals. 



Rochester shales of New York, etc. 



XXXIX. Eridotrypa Ulrich. 

 Of slender branches with more or less oblique thick-walled 

 zocecia with diaphragms which may be absent in the axial and 

 apertural regions. Mesopores with close- 

 set diaphragms, acanthopores small and 

 scarce, or wanting. Ord.-Dev. 



62. E. mutabilis Ulrich. (Fig. 188, f t 



1 9°>f-) Ordovicic. 



Slender, branching, cylindrical stems av- 

 eraging 3.5 to 4.5 mm. in diameter. Aper- 

 tures very oblique, especially in young speci- 

 mens. Small maculae commonly present 

 in older stems. Axial portion of tubes with 

 diaphragms distant about twice their diam- 

 eter. 



Trenton of Minnesota, Iowa, Wisconsin, , IG ' l , 9 " ? l0 P 0}as P n 



tilosa, enlarged. 



Kentucky, Tennessee, Ohio and Canada. 



63. E. similis Bassler. Siluric. 

 Zoarium apparently free, consisting of a pointed basal portion 



growing upward into branching stems. 



Niagara (Rochester) of Western New York and Ontario. 



XL. Stenopora Lonsdale. 

 Form varying from ramose to laminar or encrusting, with or 

 without monticules, and with wall of the zocecia periodically thick- 

 ened in the mature region ; diaphragms perforated centrally ; few, 

 irregularly distributed mesopores and large acanthopores. Miss.- 

 Mid-Carb. 



64. S. carbonaria (Worthen). (Fig. 190, £\) Carbonic. 

 Subcylindrical branches 10 to 15 mm. in diameter; surface 



smooth, no cell clusters ; apertures angular to subcircular, fre- 

 quently thick-walled, with numerous acanthopores and few meso- 

 pores. 



Coal measures of Illinois, Kansas and Ohio. 



