O’Mrara—Report on the Irish Diatomacce. 379 
Navicula latissima, (Gregory). Marine. 
Valve large, broadly elliptical; ends slightly produced, rounded ; 
intermediate free space broad, lanceolate, greatly expanded around the 
central nodule; striz linear, with moniliform striz interposed, conver- 
gent in the middle, radiate towards the ends; length ‘0060, breadth 
"0032. (Plate 32, fig. 6.) 
Gregory, Q.J.M.S., 1856, p. 40, Pl. v., fig. 4. Ralfs, in Pritch., 
p: 903, Pl. vu., fig. 70. Rab. Fl. Eur. Alg., sect. 1., p. 201: Donkin, 
N. H. Brit. Diat., p. 17, Pl. ii., fig. 2.—Pinnularia divaricata, 
O’Meara, Q. J. M.S., 1867, p. 116, Pl. v., fig. 7. 
Arran Islands, Stomachs of Ascidians, Roundstone Bay, Co. 
Galway. 
Navicula meniscus, (Schumann). Fresh water. 
Valve broadly elliptical; ends slightly produced, not capitate; 
intermediate free space narrow, except in the middle, where it 
expands into a large stauroform band, wider towards the margin than 
at the central nodule; striz linear, with moniliform strice interposed, 
convergent in the middle, radiate towards the ends; length -0026, 
breadth :0013. (Plate 32, fig. 7.) 
Schumann, Die Preussische Diat., p. 55, T.11., fig. 32. Schumann’s 
account of the locality in which the form was found by him leaves 
some doubt as to whether the deposit in which the form was discovered 
was marine or fresh water; his words are: ‘‘ In deposito Regimon- 
tano, in portu Pillawensi, in Mari Baltico. Lagerstedt, however, in- 
cludes the form among fresh-water species, under the name of Nayvyi- 
cula punctata, var. asymmetrica, Sotvat. Diat. fran Spetsbergen, p. 29, 
T. u1., fig. 7.” This figure so precisely corresponds in all respects with 
the form here described, as to render the identity perfectly certain. 
Lagerstedt states that the frustule on front view is slightly unsymme- 
trical on the longitudinal axis. This seems to me to have been acci- 
dental, arising perhaps from the valves having been separated at one 
end while adhering at the other; he adds, ‘‘ only a single specimen of 
- this variety was found.” And I have precisely the same report to 
make. So distinct is this form in its leading characters that I consider 
it a perfectly independent species, and not to be regarded as a variety 
of Nayicula punctata. 
Pond near the city of Armagh. 
Navicula lucida, N.S. Marine. 
Valve broadly elliptical, with sub-lanceolate ends; intermediate 
free space lanceolate, narrow, except in the middle, where it expands 
considerably; a strongly marked suodmarginal sulcus is present; 
strie moniliform; puncta very close; convergent in the middle; 
divergently radiate towards the apices ; length ‘0020; breadth -0012. 
(Plate 32, fig. 8.) 
Stomachs of Ascidians, Roundstone Bay, Co. Galway. 
R.I. A. PROC., SER. II., VOL. II., SCIENCE. =~ ? ili 
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