250 Proceedings of the Royal Irish Academy. 
“‘wholly destitute of a scientific basis.’ De Danske Diat., p. 27. 
Most other authors have, however, decided in favour of its validity. 
Smith’s supposition that the apices of the valves are destitute of 
silex, with Heiberg and Ralfs, I consider is founded on imperfect 
observation. 
Podosira Montagner, (Kiitz.) Marine. 
Filaments usually consisting of two frustules. Frustules large, 
cylindrical, globose at the ends. (Pl. 26, fig. 5.) 
Kutz, Bac. 52, Tr xxix.; fig. 85.°> Wis Smo B,D aay ak sepe 
63, Fl. xhx:, fig: 326. Ralfs, im Pritehs pi8ib; Piva, Glens 
Fl. Eur., p. 37. 
Arran Islands, Co. Galway. 
Podosira hormoides, (Kiitz.) Montagne. Marine. 
Frustules small, compressed. Valve with distinct umbilicus, 
obscurely punctate. 
Smith and Ralfs attribute the species to Kutzing; Heiberg, and 
Rabenhorst, Fl. Eur., to Montagne. 
Kiitz.. Bac., p. 53, Ty mexyl, fe x5,) andiery xxi eee. 
Wm: Sm,’ Be-Ds: Vol. u.,\p. 53, Ply xix ig: 327) alissanebaipche. 
p. 815, Pl. ii, fig. 45. Rab. Fl. Eur., p. 37.—Melosira hormoides, 
Heiberg, De Danske Diat., p. 29.—Podosira nummuloides, Ehr. 
Bannow, Co. Wexford. Salt ditch, near Wexford. Malahide. 
Piles on Strand, Clontarf, Co. Dublin. 
Podosira maculata, (Wm. Sm.) Marine. 
Frustules globose, distinctly punctate; puncta divided by radiate 
bands of a deeper colour, which latter do not reach the centre. 
Valves having a distinct umbilicus. (Pl. 26, fig. 5a.) 
Wm, Sm.,; B.D, Vol)aizjop. 64,°Pl) xx) tee 85) eal an 
Pnitch., p. 815. Rab-#ly Bur, p.ie7. 
Sea weeds, Bannow. Salt ditch, near Wexford. Arran Islands, 
Stomachs of Ascidians, Roundstone Bay, Co. Galway. 
Genus IV. Orruosrra, Thwaites. 
Frustules attached in filaments; without stipes, plane on the side 
view, ornamented with a circlet of puncta parallel. with the suture; 
junction surfaces spinous. 
The genus Orthosira was originally established by Thwaites, for 
the purpose of distinguishing the filamentous species with level end 
surfaces from those included in Melosira, the end surfaces of which 
are more or less arched, and thus defined it has been adopted by most 
