596 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
Terminology . — The zooecia parallel to each other are called oriented. They 
are generally axial or marginal. 
The nonparallel zooecia, erect in every meaning of the word, are the cumulate 
zooecia. Sections through such zoaria are very complicated and very difficult to 
comprehend. 
The complete zooecia, the more exterior ones, are the superficial zooecia; they 
give the better characters for classification, but they are often broken on the 
fossils. 
The deep zooecia separate the superficial zooecia, but at a lower level; their 
frontal is buried; their apertura and their avicularia are alone visible. Often 
their avicularia are more salient than those of the superficial zooecia because they 
endeavor to reach the level of the latter. 
The zoarial surface is in perpetual growth; the formation of the zooecia is 
not simultaneous; there are therefore some incomplete zooecia. These are cavities 
of greater or less size, which must not be confused with the avicularia. 
The interzooecial avicularia are very large. Their mandible is symmetrical 
and articulates on a pivot or on two lateral denticles. These avicularia bear some 
powerful muscles and they are adjacent to the superficial zooecia. 
The frontal avicularia of the deep zooecia appear interzooecial when they are 
very salient; but they remain always attached to the deep zooecia, and they are 
completely isolated from the superficial zooecia. 
Waters has best studied the classification of the Cellepores. In 1913 he gave 
a first grouping, which certainly will be perfected in the future. The table below 
sums up his opinion. 
Scliizostomatous division (=Schismopora MacGillivray, 1888) : 
C. coronopus-pumicosa group (Cellepora Waters, 1915; Cellepora Levinsen, 1909; Osthimosia 
Waters, 1913). 
0. eatoncnsis group ( Osthimosia Juilien, 18S8; Waters, 1904, not 1913). 
C. costazzii group ( Costazzia Neviani, 1S95; Lagenipora Waters, 1899; Siniopelta Levinsen, 
1909). 
Holostomatous division ( =Holostoma , MacGillivray, 1888) : 
C. descostilsii group ( Holoporella Waters, 1905). 
C. sardonica group. 
G. ramulosa group. 
To this we add a third division : 
Clithridiate division : 
Acanthionella Canu and Bassler, 1917. 
Kleidionella Canu and Bassler, 1917. 
We will adopt provisionally this classification and will discuss the names 
adopted for each genus. But the natural classification may only be made by the 
application of our system of physiological functions and in considering before all 
the connection of the operculum with the ovicell. It will be necessary to commence 
this work on the recent species. 
