O’Mrara—Report on the Irish Diatomacce. 267 
Actinoptychus senarius, (Ehr.) Brackish or marine. 
Valve divided into six compartments, areolate, arcole more or 
less hexagonal. In this species the valves vary considerably in size. 
hr, Mice., T. xxi., fig. 18, 4.b, Kitz. Bac., p. 134, T.1., fig: 21, 
T. xx1., fig. 26. The form there described does not differ from that 
which the same author has described and figured as Actinocyclus undu- 
latus, Bac., p. 182, T.i., fig. 24. .Ralfs, in Pritch., p. 839, Pl. ix., fig. 
132.—Actinoptychus undulatus, Rab. Fl. Eur., sect. 1, p. 35.— 
Actinocyclus undulatus, Wm. Sm., B. D., Vol.i., p. 25; Plate v., fig. 
43. Heib. De Danske Diat., p. 37. Cleve, Om Svenska och Norska 
Diat., p. 218. 
Salt ditch near Wexford. Bannow, Co. Wexford. Rostrevor, 
Co. Down. Stomachs of Pectens, Dalkey. Dollymount. Portmarnock, 
Co. Dublin. Sea shore, near Ballysodare, Co. Sligo. 
Var. denarius, (Ehr.) Marine. 
Compartments ten in number. Ehr. Mic., T. xviii, fig. 23. 
From stomachs of Ascidians, Roundstone Bay. Arran Islands, 
Westport Bay, Co. Galway. 
Var. duodenarius, (Khr.) Marine. 
Compartments twelve in number. Ehr. Mic., T. xvii. f. 24. 
Ralfs, in Pritch., p. 840. Weisse, Bulletin de L’Academie Imp. de 
St. Petersbourg, Tome xii., p. 122, T.1i., fig. 8—Actinocyclus duo- 
denarius, Wm. Sm., B.D., Vol. u1., p. 86. 
From stomachs of Ascidians, Roundstone Bay. Arran Islands, Co. 
Galway. 
Var. sedenarius, (Ehr.) Marine. 
Compartments sixteen in number. Ehr. Mic., T. xviil., fig. 26. 
Weisse, Bulletin de L’Academie Imp. de St. Petersbourg, Tome xii., 
p. 122. T.i., fig. 9.—Actinocyclus sedenarius, Wm. Sm., B.D., 
Vol 1:;"p. 86: 
Sea-weeds, Bannow, Co. Wexford. Arran Islands. From sto- 
machs of Ascidians, Roundstone Bay, Co. Galway. 
Var. vicenartus, (Ehr.) Marine. 
Compartments twenty in number. The only specimen of this 
variety found by me has marginal teeth obvious on some of the com- 
partments, though not noticeable on others, owing perhaps to the 
circumstance of the valve not lying quite parallel to the side. These 
teeth disappeared altogether when the form was mounted in balsam. 
Ralfs, in Pritch., p. 840. Weisse, Bulletin de L’Academie Imp. 
de St. Petersbourg, Tome xii., p. 122. 
Drehidnamaud, Co. Kerry. 
R.I.A. PROC., SER. II., VOL. II., SCIENCE. 2M 
