Members oi this group grow from a conical spitz 
with two porous walls united by radial bars. The 
more highly developed forms show, in their upper 
parts, replacement of the simple radial bars by a 
trabecular mesh. Our recent results indicate 
transference of several species from this to the 
next following order; but further research is 
needed before the position of numerous species 
can be decided. Among forms which appear 
definitely to belong to this order are the various 
species of Dictyocyathus and the species Proto- 
pharetra graphica. 
Order Metacyathina (Bedford). The discovery of 
the spitzes of this order, in the form of a small 
conical tube with transverse partitions, is referred 
to in the present Memoir. As the tube enlarges, 
rod-like processes grow from the partitions, and, 
later, the partitions appear to give rise to “dis- 
sepiments” and the rods to trabecular tissue. In 
the most characteristic members of the Metacya- 
thina, such as the genera Metacyathus, Metaldetes, 
and Metacoscinus, whilst the basal portions have 
the above-mentioned trabecular and disepimental 
structure, without inner wall or central cavity; the 
6. 
upper portions develop inner wall and central 
cavity and the irregular trabecular tissue gives rise 
to clearly-defined radial septa. Besides the above- 
named genera, Syringocnema is found to grow 
from a spitz of similar character, and it is quite 
possible that some species hitherto referred to 
“Spirocyathidae” may be members of this order. 
Present indications point to the order being more 
extensive and important than was at first suspected, 
Among genera which are perhaps members of the 
Metacyathina, but as to which further investigation 
is necessary, may be mentioned Paranacyathus. 
Paracoscinus, Pycnoidocoscinus, Ardrossacyathus, 
Metaldetimorpha. It appears to be definitely 
ascertained that regular septate cups may arise 
from two entirely different types of spitz, and this 
fact makes satisfactory classification very difficult. 
The position of Exocyathus is not yet clear. 
Order “Archaeocyathina.” The spitz, whilst still 
quite small, shows porous outer and inner walls. 
uniled by straight, porous, radial septa. Typical 
genera are “Archacocyathus,” Bronchocyathus, and 
Coscinocyathus. 
