O’Mrara—Report on the Irish Diatomacec. 263 
Ralfs, in Pritch., p. 818, considers this form may be identical with 
Melosira nivalis, but it plainly belongs to the genus Coscinodiscus. 
Lough Neagh, near Lurgan, County Armagh. Lough Island-Reavey, 
County Down. River Blackwater, near Kells, County Meath. 
Coscinodiscus Normannt, (Greg.) Marine. 
Cellules on the the disk small, obscurely hexagonal, radiate, 
arranged in fascicles of about six lines, decreasing in size as they ap- 
proach the margin ; valve very convex in the centre. 
Greville, Q. J..M.S..,. ,Vol., vil.,-p..815.Bly vi. fig. 3. _Ralfs, in 
Pritch., p. 830.—Coscinodiscus fasciculatus, O’M., Q. J. M. 8., New 
Series, Vol. vu., p. 249,. Pl. vai, fig: 1. 
Arran Island, County Galway. Stomachs of Ascidians, Roundstone 
Bay, County Galway. 
Coscinodiscus nitidus, (Greg.) Marine. 
Margin of the disk striated, cellules distant, roundish, large, dis- 
tinctly radiate, except near the centre, where they are slightly con- 
fused. Smaller at the margin, gradually increasing in size towards 
the centre. 
Greg. Diat. of Clyde, p. 27, Pl. x., fig. 45. Ralfs, in Pritch., 
p. 833, Pl. viu., fig. 18. 
Arran Island. Stomachs of Ascidians, Roundstone Bay, County 
Galway. Malahide, County Dublin. Rostrevor, County Down. Kilkee, 
County Clare. 
Coscinodiscus Gregorti, N.S. Marine. 
Margin of the disk striated, cellules sub-quadrangular, much 
smaller than in the former species, and more equal in size, radiate ; 
a small vacant angular space in the centre, from the angles of which 
so many lines of cellules run to the margin, the interspaces filled up 
by rows of cellules, gradually shortening. (Pl. 26, fig. 23.) 
Gregory, Diat., from Glenshira Sand, Q. J. M.S., Vol. v., Pl. i., 
fig. 50. After describing Coscinodiscus nitidus, Gregory remarks, 
‘‘this pretty disk was figured, without a name, in my last Paper on 
the Glenshira Sand (Trans. Mic. Soc., Vol. v., Pl. 1., fig. 50). Having 
found it tolerably frequent in Lamlash Bay, I now figure a perfect 
example, which provisionally I refer to Coscinodiscus.” JDiat. of 
Clyde, p. 28. This form may easily be confounded with the preced- 
ing, as Gregory has done ; but a more careful comparison of the many 
specimens that have come under my observation convinces me the 
forms are distinct ; and accordingly I give to the present the name 
of Gregory, who first discovered it. 
Arran Island. From stomachs of Ascidians, Roundstone Bay, 
County Galway. Stomachs of Ascidians, County Clare. 
