NORTH AMERICAK LATER TERTIARY AXD QUATERNARY BRYOZOA. 113 



Group 2. MICROPORELLAE Canu and Bassler, 1917. 



(See Bulletin lOG, U. S. National Museum, p. 417, for description and illustration). 



In this group the orifice of the compensatrix (frontal pore, micropore or asco- 

 pore) is distinct and removed from the apertura. The ovicell is hyperstomial and 

 always closed by the operculum. Dietellae are present. 



Historical. — The presence of a frontal micropore was considered by Hincks as 

 an important family character, but the study of the larvae does not permit the 

 adoption of his conclusion. According to Jullien, the ascopore is the orifice of a 

 horn-shaped body, allowing the exterior to communicate with the tentacular 

 sheath. Harmer and Levinsen believed that this was an optical illusion and that 

 the ascopore was really the orifice of the compensatrix. 



Levinsen, 1909, did not recognize the different genera established by authors 

 according to the form of the apertura. We again follow the same principles of 

 generic distinction by considering the great variations of the function of calcifi- 

 cation. Many species considered at first to belong to the Microporellae have since 

 been recognized as true representatives of the Adeonidae. According to the nature 

 of the calcification and the form of the aperture, we class the following genera in 

 this group: 



FenestruUna Jullien, 1888. 



Microporella Hincks, 1877. 



Calloporina Neviani, 1895. 



finversiula Jullien, 1888. 



Genus FENESTRUUNA Jullien, 1888. 



1888. FenestruUna Jullien, Mission scientifique du Cap Horn, 1882-83, VI, Zoologie, Brj'ozoaires, 

 p. 37. 



The frontal is garnished with stellate tremopores. The operculum closes the 

 ovicell. No avicularia. Fourteen to fifteen tentacles. 



Genotype. — FenestruUna {Cellepora) malvsi Savigny-Audouin, 1826. 



Range. — Helvetian-Recent. 



The known species belonging to this genus are: 



FenestruUna (Cellepora) malusi Audouin, 1826. 



FenestruUna {Microporella) proxima Waters, 1904. 



FenestruUna {Microporella) exigua Waters, 1904. 



FenestruUna {Microporella) parvipora Waters, 1904. 



