BRYOZOA—CRYPTOSTOMATA. 165 



cated posterior margin somewhat raised ; line of junction between 

 zocecia marked by ridge ; plain, elongate triangular space below 

 aperture. Miss. 



159. W. spinosa Ulrich. (Fig. 214, i.) Mississippian. 

 Elongate branches 3 or 4 mm. wide, 0.5 to 0.8 mm. thick ; 



acutely elliptical in section ; margins subparallel, with a series of 

 slender spines, pointing obliquely upward. 

 Keokuk of Illinois and Iowa. 



XCIV. Lichenalia Hall. 

 Subcircular, unilaminar expansion, with prostrate, elongate sub- 

 rhomboidal zocecia, having direct subtubular vestibules and rounded 

 apertures with peristome much elevated on posterior side. Sil. 



160. L. concentrica Hall. (Fig. 215.) Siluric. 

 Cup-form in young, flattened at maturity, and variously contorted 



from irregular growth or accident ; concentrically striate and rugose 



Fig. 215. Lichenalia concentrica, with enlargement of fragment. (After Hall.) 



surface on non-celluliferous side ; apertures in concentric lines, 

 opening on summit of elevated pustules. 

 Niagara of New York, etc. 



XCV. Diamesopora Hall. 

 Ramose, of hollow stems, lined internally by an epitheca ; simple 

 hexagonal or rhomboidal zocecia with oval orifices in anterior half 



