BRYOZOA—CYCLOSTOMATA, TREPOSTOMATA. 127 



XXV. Botkyllopora Nicholson. 



Disk-shaped, often coalescing, attached bodies, the apertures in 

 two rows on elevated radiating ridges, increasing by bifurcation or 



implantation towards margin. 

 No lunaria. Devonic. 



35. B. socialis Nicholson. (Fig. 



185.) Devonic. 



Alternate ridges extend to the 

 central area, others one-half to 

 two thirds that distance ; aper- 

 tures minute, often in contact or 

 inosculating. 



Hamilton of Western New 

 York, Ontario, Michigan, and the 

 Falls of the Ohio. 



Fig. 185. Botryllopora socialis, por- 

 tion of a colony much enlarged. (After 

 Hall and Simpson.) 



Order TREPOSTOMATA Ulrich. 

 XXVI. Monticulipora d'Orbigny. 



Form various, of prismatic zocecia with cystiphragms and poly- 

 gonal apertures; monticules and acanthopores occur; mesopores 

 few or wanting ; zocecial apertures polygonal ; cystiphragms in 

 mature region. Ord.-?Dev. 



36. M. mammulata d' Orb. Ordovicic. 

 .Irregularly lobate or palmate, with prominent conical or some- 

 times elongated monticules; cells of monticules of about same 

 size as others. 



Lorraine of the Cincinnati region and Kentucky. 



37. M. arborea Ulrich. (Fig. 186, a.) Ordovicic. 

 Subcylindrical branches, monticules low or absent, apertures 



with minutely granular walls bearing acanthopores. No meso- 

 pores. 



Trenton of Minnesota, Iowa, and Kentucky. 



XXVII. Atactoporella Ulrich. 

 Generally encrusting ; apertures petaloid, mesopores numerous, 

 frequently isolating the zocecia ; acanthopores very numerous. 

 Ordovicic. 



