150 Proceedings of the Royal Society 
directly connected with the outer surface of the cylindrical tube 
thus formed. More commonly, the secondary investment is open 
all down one side, and becomes directly continuous with two of 
the primary septa, thus constituting a horse-shoe shaped space, 
formed by the central tabulate area together with a wide fossula 
containing three short septa. It was shown that the fine coral 
described by Mr Billings under the name of Diphyphyllum Archiaci 
was truly a Crepidophyllum. It was further shown that two 
different forms, of very similar aspect, had been included by one 
of the authors under the name of Heliophyllum sub-ccespitosum. 
One of these forms, the typical one, is a Crepidophyllum, and will 
stand as G. sub-ccespitosum. The other is a Heliophyllum , and the 
authors described this under the name of H. elegantulum. 
The name of Thysanophyllum was proposed for a genus of 
gestrseiform corals from the Carboniferous rocks of Scotland. 
This genus is related to Lonsdaleia in the general form of the 
corallum, in the presence of an exterior vesicular zone of large- 
sized cells, and in the possession of septa, which have no con- 
nection with the outer wall. It differs from Lonsdaleia , how- 
ever, in the fact that the columella, so conspicuous in the latter 
genus, is wholly wanting, and the central area of the visceral 
chamber is occupied by strong remote, transverse tabulae. Two 
species of the genus were described, under the names of Thysano- 
phyllum orientate and T. minus. 
Finally, the genus Lindstromia was proposed for a group of 
small corals, in which the corallum is simple and conical, with an 
extremely deep calice. The septa are well developed, and meet 
in the centre of the visceral chamber, where they coalesce to a 
greater or less extent, and form a strong twisted pseudo-columella, 
which projects into the floor of the calice, and occupies a large 
portion of the entire visceral chamber. There are no tabulae, but 
the septa are furnished with more or less strongly developed 
dissepiments, which, however, are remote, and do not give rise to 
any vesicular zone. The genus may, perhaps, be regarded as 
belonging to the Aporosa. The species L. columnaris was described 
from the Devonian rocks of North America, and it was mentioned 
that the authors were in possession of other forms of the genus, 
still undescribed, from the Carboniferous rocks of Scotland. 
