356 



THE MONTICULIPOROIDS. 



form of a curved or horse-shoe-shaped line in the interior of each auto- 

 pore. In some examples of this species, the autopores are provided with 

 radially disposed pseudoseptal spines (fig. 230, d), but these are not recog- 

 nisable in other specimens. 



Of the remaining genera of the Monticuliporidce only two or three can 

 be briefly noticed here. The genus Mo?zotrypa is characterised by the 

 fact that the tubes are essentially similar to one another, being polygonal, 

 thin-walled, and furnished with few remote tabulae, while mesopores are 

 absent, as, usually, are acanthopores also. The genus ranges from the 

 Ordovician into the Devonian. Monotrypella is very similar to Mono- 



Fig. 231. — Sections of Monotrypella pulchella, E. and H., from the Wenlock Limestone of 

 Britain, enlarged about eighteen times. a, Tangential section ; b, Longitudinal section. 

 (Original.) 



trypa, but the corallites become thickened by stereoplasma as they 

 approach the surface, their walls, however, always remaining distinct 

 (fig. 231). 



The Ordovician genus Dianulites (as based upon Dianulites fastzgz- 

 atus, Eichw.) is essentially similar to Monotrypa as regards the nature 

 and structure of the corallites, but the corallum is inversely conical in 

 form, and is provided with a striated epithecal membrane, so that the 

 calices open at the upper end of the colony only, and the organism is 

 superficially quite like a simple coral in appearance. The genus Ani- 

 plexopora, ranging from the Ordovician to the Carboniferous, nearly 

 resembles Monotrypella in structure ; but numerous acanthopores are 

 developed, which often form complete rings round the autopores. 

 Dekayia, again, resembles Monotrypella in having only a single set of 

 tubes, without mesopores, but the walls of the autopores are united, and 

 there are numerous large acanthopores, the apices of which project 

 above the surface as prominent blunt spines (fig. 227). The genus is 

 only known from the Ordovician rocks. 



Lastly, in the Carboniferous and Permian genus Stenopora, the colony 

 consists of oval or circular or subpolygonal autopores, the walls of which 

 on approaching the surface become thickened with annular deposits of 

 stereoplasma, which are separated by unthickened nodes (fig. 232, c), this 

 peculiarity giving a very characteristic appearance to longitudinal sec- 

 tions. In the centre of the colony the corallites are polygonal and thin- 

 walled, and do not exhibit the characteristic annulations of the genus. 



