3 
surrounded the sun. Two of the lines in the spectrum were identical with 
those of hydrogen gas, and by directing the spectroscope to the edge of the 
sun, they could be seen simultaneously with the solar spectrum, sometimes 
overlapping it, and their position could be exactly measured. The thickness 
of this gaseous envelope was about eight thousand miles, and observations 
were in progress with a view to determine its approximative temperature. 
II. 
The Wandering Molltjse: : Dreissena Polymorphs. 
By Thomas Graham Ponton, F.Z.S. 
Read at the General Meeting, January the 7th, 1869. 
ABSTR A.CT. 
This mollusk had, said the author, well merited the name of "The 
Wanderer," for it had spread from its original habitat in the Aralo-Caspian 
Provinces throughout almost the whole of Europe. 
He then mentioned the various points at which it first appeared in 
England, and traced its progress through the country, from the period of 
its introduction in 1827, to the present time. 
A large map was exhibited on which the various localities were marked, 
where, as far as the author had been able to ascertain, it was now found in 
England and Scotland. So far as he was aware, it did not occur in 
Ireland. 
The author then described the anatomy of the animal, which had been 
previously done in a great measure by M. Van Beneden, in a paper read 
before the French Academy of Sciences, in 1825, and published in the 
Annales des Sciences Naturelles for that year. 
III. 
Tortoise Shell. 
By R. Haynes. 
Bead at the General Meeting, February the 4th, 1869. 
ABSTRACT. 
Tortoise Shell, which is a true epidermic appendage, is formed on the 
carapace of a Marine Turtle, Caretta Imbricata, popularly known as the 
Hawk's Bill Turtle, 
