O’Mrara—Report on the Irish Diatomacee. 261 
Coscinodiscus stellaris, (Roper.) Marine. 
Central rosette, consisting of five or six long and narrow cellules ; 
strie extremely minute, punctate, radiate. 
Roper; Q. J. M. 8., Vol. vi., p. 21, Pl. ii., fig, 3. Ralfs, in Pritch., 
828, Pl. v., fig. 83. 
Oyster Shells, Dublin Bay. 
Coscinodiscus concinnus, (Wm. Sm.) Marine. 
Central rosette, consisting of from three to eight large flattened 
cellules. Cellules small, radiate ; valve divided into compartments by 
radiating lines, which do not reach the margin. 
Wm. Sm., B. D., Vol. u., p.84. Roper, Q. J. M.S8., Vol. vi., pi 20, 
Pl. i., fig. 12. Ralfs, in Pritch., p.828. Roper, as above cited, statesthat 
‘the larger specimens show plainly a point that is not easily discernible 
in those under 004” in. diameter, namely a submarginal row of minute 
spines, varying from z;'s5th to zeoth of an inch apart, according 
to the size of the disk, and from each of which there is a radiating 
line almost to the centre of the valve.”’ I have, in consequence, con- 
siderable hesitation in including the species under the genus Coscino- 
discus; but, as the specimens that came under my notice were few in 
number, and in every case imperfect, I would not presume to make 
any change in the position to which it has been assigned. 
It was found by Wm. Sm. in Kinsale Bay, and fragments have 
occurred on sea-weeds, Ballybrack, and on oyster-shells from Dublin 
Bay, both in the County Dublin. 
(b). Disk with a central hyaline space like a perforation. 
Coscinodiscus perforatus, (Ehr.) Marine. 
Hyaline centre, small, surrounded by about five rounded cellules. 
Cellules large, indistinctly hexagonal, radiate, decreasing in size near 
the margin. (PI. 26, fig 20.) 
Smith describes the cellules as ‘“‘equal,’’? and Ralfs as ‘‘ minute ;” 
but in my specimens they differ as stated above. 
hr Mies Ee xvi fis?) 46% VWan. Sm} BlD.y Voli, pegs: 
Ralfs, in Pritch., p. 829. 
From stomachs of Howth Oysters, Tide-pool, Monkstown, Dalkey, 
Ballybrack ; on Oyster shells, Dublin Bay. Stomachs of Ascidians, 
Belfast Bay. 
(c). Disk without a central rosette or vacant space.  Cellules radiate. 
Coscinodiscus gigas, (Ehr.) Marine. 
Disk very large, cellules not very large, hexagonal, radiate, smaller 
towards the centre. (Pl. 26, fig. 21). 
hr, Mics le xvi me 34; sKtz:) Bas,,..p. 132, 1. 1., fig, 16. 
Stomachs of Ascidians, dredged on the coast of County Clare. 
