88 PROCEEDINGS OF SOCIETIES. 
Mr. Archer also exhibited a fine gathering, quite pure from 
other forms, of Micrasterias Thomasiana (ejus), taken from a 
pond adjacent to that in which he had found it first; since then 
he had met with this form exceedingly sparingly, hence a copious 
gathering was the more welcome. 
September 20th, 1866. 
Mr. Crowe exhibited an abundant gathering of Stephanosphera 
pluvialis and Gonium pectorale, in great beauty and activity, 
obtained from the old Bray-Head Station. The latter showed 
very varied sizes and states of division, and the whole formed a 
very handsome object. 
Rev. Eugene O’Meara, A.M., had much satisfaction in bringing 
before the notice of the Club a most interesting and productive 
gathering of diatoms, collected by Dr. E. Perceval Wright whilst 
dredging, in from fifteen to thirty fathoms, off the Arran Islands, 
in the month of August last. This contained many rare forms, 
as well as others which appeared to be new. He (Mr. O’Meara) 
had only received the material a few days ago, and, as was to be 
expected from the circumstances under which the gathering was 
made, it was very dirty, requiring much care to render it tolerably 
clean ; therefore as yet he had been able to give the material only 
a cursory examination, and would defer more detailed observation 
to some future time. He thought, however, what he had stated 
as to the value of the gathering would be justified by an inspection 
of the slide now exhibited. 
On the present occasion he would draw attention to one form 
only, which he would designate Pinnularia divaricata, and de- 
scribed it as follows:—Length of frustule about ‘0057”, breadth 
about ‘0035”. Side view broadly elliptical; the ends slightly 
produced, broad and rounded ; the central space large, its outline 
resembling the vertebra of a fish. Through this space there runs 
a well-marked median line, very fine at the outward extremities, 
but becoming broader towards the centre, at some little distance 
from which point it terminates in asmall bulb. The coste are 
arranged concentrically with the apex at both ends for about a 
fourth of the length of the frustule, and in the intermediate por- 
tion spring from the margin of the central nodule; the central 
costa runs at right angles with the longitudinal axis, and those at 
either side radiate towards the central costa more and more so as 
the distance from this line increases. The cost in the central 
portion of the valve are furcate; in some the furcation appears 
near the outer margin of the valve, in others near the central 
nodule. Some few are bifurcate. Still further it seems worth 
of attention that the coste are slightly notched by longitudinal 
