BRYOZOA—TREPOSTOMATA. 1 3 1 



49. A. cingulata Ulrich. (Fig. 186, £\) Ordovicic. 

 Ramose, of cylindrical or subcylindrical branches dividing dicho- 



tomously; no monticules; apertures subpolygonal, a moderately- 

 thin wall studded with granules between them ; groups of cells of 

 larger size; no mesopores. 



Lorraine of Kentucky and the Cincinnati, O., region. 



XXXIII. Monotrypella Ulrich. 

 Like Amplexopora, but distinguished by the absence of acantho- 

 pores. Ord.-Dev. 



50. M. (Rhombotrypa) quadrata (Rominger). Ordovicic. 

 Irregularly cylindrical branches, from 4.5 to 10.5 mm. thick, the 



tubes rhombic in section, arranged in curved diagonal lines. No 

 mesopores or monticules. 



Richmond beds of Ohio, Indiana, Illinois, Wisconsin and Mani- 

 toba. Common and characteristic. 



51. M.? arbuscula (Hall). (Fig. 187.) Siluric. 

 Fruticose, several slender (2-3 mm.) stems from a single base; 



bifurcation frequent; cell tubes very gradually diverging to surface. 

 A characteristic fossil of the Manlius limestone of New York. 



Fig. 187. Monotrypella? arbuscula. 



XXXIV. Petalotrypa Uirich. 

 Irregular, compressed, bifoliate branches or fronds, with pris- 

 matic zocecia arising from strongly flexuous mesotheca, with poly- 

 gonal apertures. Devonic. 



52. P. compressa Ulrich. (Fig. 190, a.) Devonic. 



Smooth, with scarcely appreciable clusters of slightly larger and 



somewhat more separated cells ; zocecia subpolygonal to hexa- 



