55 
from broadly deltoidal to more cuneiform in shape. There 
1$ à corresponding difference in the actual lengths of these 
axes, but their ratio is tolerably constant for each 
individual, and about as 70 to 100. The wall is 
stout except towards the summit, where it becomes 
thiuner. It is covered by a strong, coarse epitheca, 
which is faintly marked transversely by a series of 
broad ridges and corresponding but narrower depressions, 
having the same curve as the margin of the calice. The 
coste are numerous and arranged in sets in which three very 
fine ones alternate with another slightly larger. They fol- 
low the contour of the edges, but can only be traced on the 
Surface of well preserved specimens. In the deltoidal ex- 
ample figured the finer coste fade away near the lateral 
edges, while the larger ones become more prominent. On 
the surface of this corallum, which is the finest collected, I 
counted thirty-two of the larger созбе. 
The calice of an adult deltoidal specimen contains 112 
Septa of three sizes, viz., 28 stout, equal, and in appearance 
primary, an equal number thinner, but nearly as long, and 
56 still shorter and finer. The calice figured is that of the 
cuneiform corallum mentioned, and has 54 septa on one side 
aud 50 on the other. They are in 27 sets, two of which 
contain no septa of the third order. This calice is tolerably 
perfect, and a number of the primary septa, still intact, rise 
slightly above the margin. The free edges of the primary 
septa eurve downwards towards the columella, and then de- 
Scend vertically to bound the central fossa, which is deep, 
long, and moderately broad. For some distanca from their 
free edges the septa are quite plain, but lower down their 
sides are marked by closely set, radiating rows of fine gran- 
ules. The columella is a long, stout, perfectly plain, plate- 
like structure. It is in the line of the long axis, and being 
largely free it forms a conspicuous feature in the calice. 
The dimensions of the deltoidal specimen taken as type 
are: —Height, 33 mm.; length of calice, 37 mm.; breadth of 
calice, 26 mm. Тһе cuneiform specimen, of which both the 
corallum and calice are figured, is 35 mm. high, and its 
calice is 29 mm. long and 22 mm. broad. It is an extreme 
form, the other examples tending to deltoidal in outline. 
Locality, ete.—Common in the Upper Eocene or Oligocene 
of Spring Creek, Victoria. 
This species closely resembles P. deltoideus, Duncan, but 
is larger and heavier. It is also less attenuated at the base, 
while its lateral edges are characteristically convexly curved. 
Moreover, the hexameral arrangement of the septa observed 
in P. deltoideus is evidently wanting in 7". magnus. 
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