106 THE PALEONTOLOGY OF MINNESOTA. 



[Classification . 



Family Ptilodicttonid^, Zittel. 



Genera : Ptilodictya Lonsdale, Cldthropora Hall, Phcenopora Hall, Oraptodictya Uleich, Arthro- 

 pora U., TceniodictyaJJ., Ptilotrypa U., StictotrypaJJ., StietoporellaV., Intrapora Hall, Coscinella Hall. 



Family Rhinidictyonid^, Ulrich. 



Genera : Rhinidictya Ulrich, Eurydictyq, U., Dieranopora U., Ooniotrypa U., Euspilopora U., Phyl- 

 lodictya U., PachydictyaJJ., Stictopora Hall. 



Family Oystodicttonid^, IJlrieh. 



Genera: Cystodictya Ulbic&, Coscinium Keysbrling, Dicliotrypa U., ActinotrypaXH ., Tceniopora 

 Nicholson, Prismopora Hall, Scalaripora Hall, Evactinopora Meek and Wobthbn, Glyptopora U., 

 Ooniocladia Ethkidge, Acrogenia Hall. 



Family Ehinoporid^, Ulrich. 



Genus : Rhinopora Hall. 



Family Helioteypid^, Ulrich. 



Genus : Heliotrypa Uleich. 



Family Artheostylid^, Ulrich. 



Genera : Arthroatylus Ulrich, Helopora Hall, Sceptropora Uleich, ArthroQlema Billings, Nema- 

 topora Uleich, ? Thamnotrypa Hall. 



Family Ehabdomesontid^, Vine. 



Genera: Ehabdomeson Young and Young, Cceloconus Uleich, Rhombopora Meek, Nemataxis 

 Hall, Acanthoolema Hall, Bactropora Hall, 9 Tropidopora Hall. 



Family Steebloteyfid^, Ulrich. 

 Genera : Streblotrypa Uleich, Cyclopora Peout, ? Proutella Uleich, fOycloporella U. 



Family Spheagiopoeid^, Ulrich. 



Genus : Sphragiopora Uleich. 



Family Fenestellid^, King. 



Genera : Fenestella Lonsdale, Semioosoinium Peout, Fenestrapora Hall, Isotrypa Hall, Tectuli- 

 pora Hall, Unitrypa Hall, Hemitrypa Phillips, Helicopora Claypole, Archimedes LeSueue, Lyropora 

 Hall, Fenestralia Peout, Polypora McCoy, Thamniscus King, Phyllopora King, Ptiloporina Hall, 

 Ptiloporella Hall, 9 Loculipora Hall. 



Family Acanthocladiid^, Zittel. 



Genera : Pinnatopora Vine, Septopora Peout, Acanthocladia King, Synocladia King, Diplopora 

 Young and Young, Ptilopora McCoy, 9 Icthyoraehis McCoy, 9 Penniretepora d'OEBiQNY, f Ramipora 



TOULA. 



Family Phyllopoeinid^, Ulrich. 

 Genera : Phylloporina Uleich, Chainodictyon Foeestb, Drymotrypa Ulrich, 9 Crisinella Hall. 



Suborder TREPOSTOMATA, Ulrich. 

 Zooecia superimposed directly one upon the other so as to form long tubes 

 intersected by straight or curved partitions (diaphragms and cystiphragms), repre- 

 senting the covers and floors of the successive layers. Two regions are distinguish- 

 able in the tubes, an axial or "immature" region in which the diaphragms are 

 remote and the walls thin and prismatic ; and a peripheral or " mature " region in 

 which the walls are thickened and otherwise changed, the transverse partitions 

 more abundant, and accessory elements, such as mesopores and acanthopores, devel- 

 oped. ZocBcial covers with a small central orifice. 



Family Monticulipoeid^, Nicholson. 



Genera : Monticulipora d'OBBiGNY, Atactoporella Ulrich, Homotrypella Uleich, Peronopora Nich- 

 olson, Homotrypa U., Prasopora Nicholson and Ethridge, Mesotrypa U. 



