NORTH AMERICAN LATER TERTIARY AND QUATERNARY BRYOZOA. 113 
Group 2. MICROPORELLAE Canu and Bassler, 1917. 
(See Bulletin 106, 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: 
Fenestrulina Jullien, 1888. 
Microporella Hincks, 1877. 
Calloporina Neviani, 1895. 
flnversiula Jullien, 1888. 
Genus FENESTRULINA Jullien, 1888. 
1888. Fenestrulina Jullien, Mission scientifique du Cap Horn, 1882-83, VI, Zoologie, Bryozoaires, 
p. 37. 
The frontal is garnished with stellate tremopores. The operculum closes the 
ovicell. No avicularia. Fourteen to fifteen tentacles. 
Genotype.—Fenestrulina ( Cellepora) malusi Savigny-Audouin, 1826. 
Range. —Helvetian-Recent. 
The known species belonging to tins genus are: 
Fenestrulina ( Cellepora ) malusi Audouin, 1826. 
Fenestrulina ( Microporella) proxima Waters, 1904. 
Fenestrulina ( Microporella ) exigua Waters, 1904. 
Fenestrulina (Microporella) parvipora Waters, 1904. 
