287 
terior as well as the exterior surface of the wall, There is no 
epitheca, and the costz are broad, well marked, and continuous 
with the septa. . The latter are at the wall broad and spreading, 
irregular in outline, occasionally branched, and very porous ;. 
their projections into the calice taper off, and are straight, free, 
sharply defined, and imperforate. There are six systems of septa 
with three complete cycles in those at the ends of the calice, but 
with two only in the central pair. The secondaries and tertiaries 
are subequal, and the primaries both longer and stouter; all three 
orders are exsert and coarsely granular. 
The columella rises vertically from the bottom of the fossa, 
and forms the most conspicuous feature of the calice. It is 
straight and lamellar, of moderate length, and most irregular as 
to its surface, which is marginally indented, and laterally ridged, 
knobbed, and perforated. It is free from the septa except Just 
at the base, where it is apparently connected by thin processes to 
the primaries. 
Height of corallum, 6 mm.; length of calice, 6 mm.; breadth 
of calice, 5 mm. 
Locality.—Eocene at Fyan’s Ford, Geelong. One good 
example (the type) and another smaller and evidently young. 
NV. aperta is closely allied to NW. gracilis, but may be dis- 
tinguished from that species by its stouter wall, coarser septa, 
more conspicuous columella, and broader and more open calice. 
The absence of a fourth cycle of septa is, perhaps, unimportant. 
Possibly other examples may yet be found with this developed. 
EXPLANATION OF PLATES. 
Pirate IX. 
Fig. 
1. Trematotrochus complanatus—a, coralium, 8 diam.; 5, calice, 10 diam. 
2. Trematotrochus lateroplenus—a, corallum, 8 diam.; b, calice, 10 diam. 
3. Notephyllia semivestita—a, corallum, 2 diam.; 6, calice, 6 diam. 
4. Notophyllia aperta—a, corallum, 3 diam.; b, calice, 6 diam. 
PuaTE X. 
Fig. 
1. Stephanophyllia implexa—a, corallum, 3 diam.; b, calice, 6 diam.; 
c, section of base, showing one system of costz, 10 diam.; d, a 
primary septum, magnified. 
2. Notophyllia gracilis—calice, 6 diam. 
3. Notophyllia gracilis, var.—a. corallum, 3 diam.; b, calice, 6 diam. 
