PROCEEDINGS OF SOCIETIES. 167 
descriptions in Pritchard; but it at least was the first instance of 
any species of the genus having been shown at the Club. 
Mr. Archer showed specimens of Gonionema velutinum (Nyl.), 
for the loan of a specimen of which apparently very rare lichen 
he had to thank Admiral Jones. Mr. Archer showed the apothe- 
cia under a low power as an opaque object, and a small fragment 
of the thalius under a higher power. He likewise showed a frag- 
ment from the only fertile specimen of Scytonema myochrous which 
he had ever found, for the purpose of comparison, to show the 
great affinity in the thalloid structure of the two plants; but there 
could not be a doubt of their being utterly specifically distinct, 
both to the naked eye and under the microscope. 
Dr. E. Perceval Wright exhibited a section of a substance found 
encrusting the human bladder in a case that came under the no- 
tice of Dr. Fleming. The general appearance of this substance 
was that of a rough nodulated mass, dense in structure, and of a 
hard, bony-like appearance. On examination of sections made of 
the substance itself, as it was taken out of the bladder, and also 
after long maceration in dilute hydrochloric acid, it revealed no 
true bony structure; and although Dr. Hassall had written that 
he had discovered bone-cells in this substance, yet Dr. Wright 
could not agree with him as to their existence, nor did he think 
the members of the Club would either. True bone owed its origin 
in the adult being either to a conversion from cartilage or to a 
development from periosteum ; and structures that arose from the 
surface of an altered mucous membrane should not be regarded as 
bone, but as calcareous deposits. Rokitansky had called such 
structures by the name of anomalous bone, but this was likely to 
mislead. The point to be insisted on was that such structures 
a not developmentally or histologically to be considered as 
one. 
Mr. Crowe showed fine and numerous specimens of Campylo- 
discus. 
Captain Hutton showed a specimen of Arachnoidiscus ornatus 
found by him in a gathering lately made at Malahide; this would 
make the second record of any form of Arachnoidiscus being found 
in Britain. Captain Hutton had had but once in his possession 
foreign specimens of this form, and that long ago. His tubes and 
apparatus had been much used since, and it could not, therefore, 
be at all probable that this specimen could have remained attached 
to a dipping-tube ever since, and now made its appearance. He 
believed that the present was a genuine instance of the occurrence 
of this fine form in Ireland, and he was the more inclined to feel 
certain of its reality in that Arachnoidiscus had been already found 
by Ralfs in the south of England, though it had been questioned 
that he had made some mistake by the accidental intrusion of a 
foreign example. 
