8 
NATURAL SCIENCES OF PHILADELPHIA. 
February \Qih. 
Vice President Bridges in the Chair. 
Thirty-nine members present. 
Mr. Ashmead called the attention of members to a Marine Alga which he 
had discovered about three years since at Beesley's Point. From the micro- 
scopic structure of the frond, he supposed it to be a Callithamnion, and not 
finding it described in Nereis Boreali- Americana, he concluded it was a new spe- 
cies. He had referred it to the late Prof. Bailey, of West Point, who returned 
it with the remark, " I cannot make this agree with any Callithamnion known 
to me ; if it were truly dichotomous, I should refer it to Griffithsia setacea^ but 
without its fruit I cannot decide what it is. It is an interesting plant, and 
ought to be watched for, at different times in the year, so as to secure its fruit." 
During the past summer, I collected, at Beesley's Point, quite a number of 
specimens of this plant ; I found them growing in shallow water, attached to 
old shells and other submerged substances ; but I found none in fruit. Upon 
the examination of a number of specimens, I formed the conclusion that the 
plant belongs to the genus Griffithsia, and is a new species. Under this impres- 
sion, I sent specimens to Prof. Harvey, of Trinity College, Dublin, for examina- 
tion. I recently received a letter from that distinguished Algologist, and though 
not with a view to publication, I presume an extract may be presented without 
impropriety. Dr. Harvey says : " The supposed new Griffithsia, sent in one of 
your parcels, is Griffithsia tenuis^ J. Ag., identical with the specimens in my her- 
barium, from Agardh himself. The American plant is a little stronger in growth 
than the European, but I see no character to separate it. The fruit is unknown. 
Your specimens are not in fruit. The genus to which it belongs is therefore 
doubtful ; and I am therefore disposed to think that it will turn out to be a 
Callithamnion — an opinion I arrived at, because it is very closely allied to Calli- 
thamnion thysigerum^ of Australia and Ceylon, the fruit of which is known to 
me. Indeed, it is possible that Callithamnion thysigerum itself may be only a 
variety of Griffithsia tenuis.'' This alga is interesting as an addition to the 
marine flora of the American coast. 
Mr. Lesley described a curious reverse drainage of the uplands bordering the 
Ohio river on each side, near Ironton, and within the limits of the coal region of 
southern Ohio and Kentucky. On climbing the river cliffs about 300 feet, the 
summit is found to be formed by a stratum of conglomerate about fifty feet thick, 
and one looks over into bowl-shaped heads of small valleys, delivering their 
waters backward, and only reaching the river by circuits more or less extensive. 
These valley heads*are so close to the great river valley, that short tunnels driven 
along in the almost horizontal coal-beds would suffice to bring out the ores which 
crop around them. The barriers are lofty knife edges or thin walls, or strips of 
horizontal conglomerate, the place of which in the coal measures is about 500 
feet from the bottom. The dip of the strata is only about thirty feet to the mile, 
and contrary to the current of the river. It would be difficult, he thought, to 
explain this structure by the popular theories of denudation, or any bypothethis, 
unless subaerial deluges. 
Mr. Powel protested against the too constant recourse to immediate volcanic 
agency in explaining geological phenomena. In the Pottsville region the strata 
were often folded and contorted by side pressure from various causes, with no 
close or immediate local evidence of volcanic agency, it being often seen only far 
off. The structure of the Ohio valley now mentioned, might have occurred ori- 
ginally as a mere crack in the conglomerate, perhaps caused by a very trifling 
local upheaval, or a slight shrinkage, or even a subsidence at a distance, this 
would determine the original line of drainage, and attrition might, in time, pro- 
duce such a valley as Mr. Lesley had described. 
[Feb. 
