198 
THE GEOLOGIST. 
like the fossils of Archasocidaris to whicli I sliall presently allude. This 
specimen appears to have been stripped of its spines before beins; buried 
in the sand. I have, however, found in the same bed, and near the same 
place, a fevr detached plates and the casts of what appear to be spines. I 
also find traces of large plates in some of the friable shales near it. The 
fossils associated with this specimen are not numerous. I have sent up a 
good specimen of Psammodus porosus from the same bed. In the lime- 
stone which underlies the sandstone there arc a great abundance of fossils, 
of which by far the most characteristic are remains of Archccocidaris, whicli 
occur in the greatest profusion. They are found in groups of plates and 
spines ; nearly all of these groups present more or less the same assem- 
blage of hexagonal and pentagonal plates, the former tubercled, with nu- 
merous spines both smooth and muricated, giving the idea that each of 
these groups represents the remains of one or more of these animals as 
they fell to pieces. In no case do I find among these any pentagonal 
plates provided with tubercles like those of the cast in the sandstone ; and 
accordingly differing, as it does, from both Pala3chinus and Archa^ocidaris, 
I think that there can be no doubt that it is a new addition to the Echino- 
derms of the carboniferous period. — The paper was illustrated by a careful 
drawing of the specimen on an enlarged scaJe, for which the society was 
indebted to the kindness of Mr. Bailey, who, on being called on by the 
President, observed, that in his opinion the fossil belonged to the genus 
Archaiocidaris, but was certainly a new species. He was led to this con- 
clusion from the fact that the whole family of the Cidaridse presented an 
appearance like that shown on the specimen, viz. that the plates exhibited 
one large tubercle. In the more recent specimens all the plates were tu- 
bercled, while in this Palaeozoic fossil the tubercles only appeared on a 
few of them. He would only observe, in conclusion, that the society owed 
a great deal to Mr. Harte, by whose care and diligence this fossil had been 
discovered and laid before them, like many others which they had received 
from the same localit}^ within the last few years. 
Mr. Emerson Reynolds then read a short communication upon " Thalli- 
ferous Pyrites, from Ballydehob, county Cork." He said that he had ex- 
amined several Irish ores for this element since he had laid his last notice 
on this subject before them in 1863, but that the present specimen was the 
only one in which he had succeeded in discovering thallium, and here only 
in small quantity. 
Geological Society. — April 13. — 1. " On the Geology and Mines 
of the Nevada Territory." By Mr. W. Phipps Blake. — In describing the 
physical features of the country, the author observed that it is an elevated 
semi-desert region, composed of a succession of longitudinal mountain- 
ranges with intermediate valleys and plains, the most abundant rocks 
being metaraorphic and igneous ; but Tertiary strata and Carbonifero\is 
Limestone also occur. 
The author then described the hot springs, which are extended along a 
line of fissure in a granitic rock, and parallel to the mountains, and which 
deposit silica in an amorphous and a granular state, sulphur being also 
seen in the cracks and cavities of the siliceous de2)0sit. He considered 
these phenomena to illustrate the formation of a quartz-vein in a fissure. 
Mr. Blake then gave an account of certain mineral veins in porphyry, 
which yield sulphurets of silver (including crystals of Stephanite, but very 
little ruby silver) and a little gold ; also galena, copper pyrites, iron 
pyrites, and a little native silver, the veinstone being a friable quartz. The 
