American Palceozoic Bryozoa. 



153 



Phyllodictya, Ulrich. — Zoarium forming simple leaf-like expansions, 

 sometimes partially and very irregularly branched. Cell-apertures 

 small, oblique, with the lower margin lipped. Interstitial spaces 

 minutel}' granular or punctate. Trenton. 



Family MonticuliporidcB. Nicholson. 



Monticulipora, D'Orb. Zoarium submassive, incrusting, or irregu- 

 larly frondescent. Surface with monticules, or smooth. Cells poly- 

 gonal, apparently of one kind only. Tubes crossed by straight dia- 

 phragms and at intervals cystoid diaphragms are developed. Spiniform 

 tubuli more or less numerous. Trenton and Cincinnati. 



Sub-genus Trematopora, Hall. — Ramose to sub-frondescent, with or 

 without monticules. Interstitial cells few, sometimes gathered into 

 groups. Tubes throughout the greater portion of their length "imma- 

 ture," and provided with few or no diaphragms ; just before opening 

 at the surface cystoid diaphragms are developed. Cincinnati and Nia- 

 gara. 



Peronopora, Nicholson. — In double leaves. Interstitial cells and 

 spiniform tubuli more or less numerous. Tubes with numerous cystoid 

 diaphragms. Interstitial tubes provided with closely arranged straight 

 diaphragms. Cincinnati. 



Prasopora, Nicholson and Ethridge. — Free, or loosely adhering to 

 foreign objects, forming hemispherical masses, or thin expansions, 

 with a wrinkled epitheca covering the lower surface. Tubes cyclin- 

 drical or prismatic, and having one or both sides lined with cystoid 

 diaphragms. Interstitial tubes often completely isolating the proper 

 zooecia, and crossed by numerous diaphragms. Spiniform tubuli 

 sometimes nearly absent, in other cases more numerous. Trenton and 

 Cincinnati. 



Diplotrypa, Nicholson. — Zoarium free, hemispherical. No spini- 

 form tubuli. In other respects like Prasopora, excepting that the 

 tubes are provided with straight diaphragms onlj*. Niagara. 



Monotrypa, Nicholson. — Irregular, hemispherical, or globular 

 masses. Surface smooth, or with low monticules carrying groups of 

 larger cells than the average. Tubes thin-walled, prismatic, and 

 traversed by straight diaphragms. No interstitial cells nor spiniform 

 tubuli. Trenton to Carboniferous. 



Monotrypella, Ulrich. — Ramose, smooth or tuberculated. Cells 

 apparently of one kind only. Walls very thin in the axial portion oi' 

 the branches, but much thicker in the peripneral region. Diaphragms 

 straight. No spiniform tubuli. Trenton and Cincinnati. 



