O'Meara — Report on the Irish Diatomacece. 2QS 



Ealfs, in Pritch., p. 818, considers this form may be identical Tvitli 

 Melosira nivalis, but it plainly belongs to the genus Coscinodiscus. 



Lough Neagh, near Lurgan, County Armagh. Lough Island-Iteavey, 

 County Down. Eiver Blackwater, near Kells, County Meath. 



Coscinodiscus Normcmni, (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., Yol. vii., p. 81, PL vi. fig. 3. Ealfs, in 

 Pritch., p. 830. — Coscinodiscus fasciculatus, O'M., Q. J. M. S., New 

 Series, Yol. vii., p. 249, PL vii., fig. 1. 



Arran Island, County Galway. Stomachs of Ascidians, Eoundstone 

 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. Ealfs, in Pritch., 

 p. 833, PL viii., fig. 18. 



AiTan Island. Stomachs of Ascidians, Eoundstone Bay, County 

 Gal way. Malahide, ^County Dublin. Eostrevor, County Down. Kilkee, 

 County Clare. 



Coscinodiscus Oregorii, IS". 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. (PI. 26, fig. 23.) 



Gregory, Diat., from Glenshira Sand, Q. J. M. S., Yol. 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, Yol. v., PI. i., fig. 50). Having 

 found it tolerably frequent in Lamlash Bay, I now figure a perfect 

 example, which provisionally I refer to Cosciaodiscus." Diat. of 

 Clyde, p. 28. This form may easily bo 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, Eoundstone Bay,. 

 County Galway. Stomachs of Ascidians, County Clare. 



