238 
perhaps may constitute another species. The characteristics or the 
four species, as these are defined by Studer, are given in the 
following table: 
species 
pileus 
tiara 
concentrica 
philippinensis 
Thickness 
of corallum 
20-30 mm 
12 -20 mm 
13- 18 mm 
15—18 mm 
15 mm 
Theca 
9 
with numerous 
irregularly 
scattered 
pores 
with 
scattered 
pores 
Strongly 
perforated 
Costae 
Sharp spines 
on radially 
arranged 
costae 
radially 
arranged 
with smooth 
pointed spines 
radially 
arranged 
with pointed 
conical spines 
marginal 
part radially 
arranged; 
spines small, 
rough 
Septa 
strongly 
prominent, 
thick; 
strongly 
inciso-dentate 
thinner 
than in 
H. pileus 
thin and 
delicate; 
deeply serrate 
thin 
♦ 
Calicles 
central 
calicle 
very little 
more distinet 
than the 
secondary 
calicles 
central 
calicle 
little more 
distinet 
than the 
secondary 
calicles 
central 
calicle 
large; 
secondary 
calicles in 
almost regular 
concentric 
rows 
central 
calicle 
large; 
secondary 
calicles in 
irregular 
concentric 
rows 
Septa of the 
secondary 
calicles 
strongly 
prominent 
prominent, 
but less than 
in H. pileus 
prominent 
strongly 
prominent 
Columella 
papillary 
rudimentary 
p 
wholly 
rudimentary 
(Studer, 
p. 414); spongy 
in the bottom 
of the calicles 
(Studer, 
p.415) 
