46 
DESCRIPTION OF NEW SPECIES 
Tettadium cylindricum n. sp. 
Plate III, figure 3 
Figure 5. A. Cross section of an average cylindrical eorallite. 
B. Cross section of a mature eorallite, showing the tendency to 
become four-sided. 
C. Budding of young eorallite. 
This Tetradium is similar to Tetr odium cellulosum in every 
respect except in the shape of the average eorallite. When 
growing singly or on the edge of a ‘bundle’ there is a marked 
tendency to a cylindrical form, whereas the mature eorallite of 
Tetradium cellulosum is four-sided. Also, in the few specimens 
at hand there appears to be less of a tendency to closely unite 
in bundles, and there is a larger proportion of individual coral - 
lites. A larger collection, however, might show this to be an 
accidental feature. 
The young eorallite buds from the mature one, enlarging its 
diameter fairly rapidly; it continues its growth, in the majority 
of cases, in the same cylindrical form. The walls of some 
specimens, in advanced age, thicken half-way between the septa, 
resulting in a tendency to a four-sided eorallite. The Lowville 
species Tetradium cellulosum in its nepionic stage has the same 
cylindrical form, but each eorallite soon assumes the typical 
Tetradium form. The Lowville species, apparently, is the direct 
descendant of the Chazy species. 
Formation and Locality. Chazy: Aylmer limestone. Mac- 
Laren landing. 
