574 Studer: Bericht über die Leistungen 



they are partially separated by the intervention of the smaller 

 corallites whicli are always angular in shape, have thin walls, 

 are never so far developed, as lo completely isolate all the 

 larger tabes, and are always provided with more numerous 

 and more closely set tabulae than is the case in the latter. 

 Spiniforin corallites präsent or absent. 



Type of the group: Monticulipora petropolitana Fand. 



3. Subg. Monotrijpa. Corallites of one kind only, so far as their 



internal structure is concerned; though there may be well 

 marked Clusters (or monticules) of tubes, appreciably larger 

 than the average. Corallites usually conspicuously prismatic, 

 their walls thin an apparently structurcless, or retaining their 

 primitively duplex character. Spiniform corallites mostly 

 wanting. Tabulae complete, uniforraly distributed through-out 

 all the corallites, without respect to the size of these; someti- 

 mes nearly obsolete. 



Type Monticulipora imdulata Nich. 



4. Subg. Prasopora Nicli. and EtTi. jun. Corallites of two kinds, 



the sraaller ones interspersed throughout the colony, or partially 

 aggregated into Clusters. Large tubes with peculiarly incom- 

 plete tabulae, which form a series of marginal vesicles, enclosing 

 a lateral space which is usually crossed by a few straight tabu- 

 lae. Spiniform corallites wanting, or very sparingly developed. 

 Walls of the corallites thin and apparently structurcless. Coral- 

 lum usually discoid. 



Type. Prasopora Grayae Nich. and Etil. jun. 



5. Subg. Peronopora Meli. Corallites of two kinds, the larger 



ones with tabulae of the same peculiarly incomplete type as in 

 Prasopora. Small tubes with dose set tabulae. Walls of the 

 corallites thickened and apparently more or less completely 

 amalgamated, so that their primitive duplex character is lost. 

 Spiniform corallites usually largely developed. Corallum lami- 

 nar or incrusting. 



Type: M. frondosa d'Orh. 



Capitel 6 behandelt die einzelnen Species der ob- 

 genannten Subgenera, jede durch Tafeln und Holzschnitte 

 erläutert. 



Neue Arten: Heterotrypa Anäreivsii Cincinnati Group. 



Ohio. 



Heterotrypa ülricJiii Cincinnati Group. Ohio. 



//. Dawsoni Cincinnati Grop. Ohio. 



K Trentonensis, Trenton Kalk v. Petersboro. Ontario. 



