MICROPORA. 1 73 



the membranous area on the front of the cell, a character 

 in which it agrees with the forms grouped under the old 

 genus Lepralia ; while, on the other hand, the elevated 

 margin of the zocecium indicates its affinity with the 

 Membraniporae. 



Genus MICROPORA, Gray. 



Der. From pticpos, small, and ir6pot, an opening. 



FLUSTRA (part.), Johnston. 

 DISCOPORA (part.), Lamarck. 

 MICKOPORA, Gray, B.M. Bad. 115: Sniitt. 

 MEMBHAXIPOUA (part.), Busk, &c. 

 LEPRALIA, sp., Norman : Reuss. 

 REPTESCIIAKEI.I.I.NA (part.), D'Orbigny. 



GENERIC CHARACTER. ZOARIUM incrusting. ZO<ECIA 

 with prominent raised margins; front depressed, wholly 

 calcareous; orifice semicircular or suborbicular, inclosed 

 by a calcareous border. 



IN this genus the zooecia agree with those of Membra- 

 nipora in the possession of a raised margin and depressed 

 front; but there is no trace left of the membranous 

 covering, while the orifice, which is placed at the very top 

 of the cell, is bounded above and at the sides by the margin 

 of the wall, and below by a calcareous rib or border. 

 Avicularia are present in some species, and wanting in 

 others. 



Besides the three species described in this work, a con- 

 siderable number of Mernbranipora, both fossil and recent, 

 must be referred to this group. 



Several Miocene forms have been recorded; and the 

 generic type is as old as the Chalk at least. 



