250 Proceedings of the Royal IrisJt Acadeui)/. 



"wholly destitute of a scientific basis." De Danske Diat., p. 27. 

 Most other authors have, ho-werer, decided in favour of its validity. 

 Smith's supposition that the apices of the valves are destitute of 

 silex, -with Heiberg and Ealfs, I consider is founded on imperfect 

 observation. 



Podosira Montagnei, (Ktitz.) Marine. 



Filaments usually consisting of two frustules. Frustules large, 

 cylindrical, globose at the ends. (PI. 26, fig. 5.) 



Kiitz. Bac, 52, T. xxix., fig. 85. Wm. Sm. B.D., Yol. ii., p. 

 53, PI. xlix., fig. 326. Ealfs, in Priteh., p. 815, PI. v., fig. 61. Kab. 

 PI. Eur., p. 37. 



Arran Islands, Co. Galway. 



Podosira hormoides, (Kiitz.) Montague. Marine. 



Frustules small, compressed. Yalve with distinct umbilicus, 

 obsciu-ely punctate. 



Smith and Ealfs attribute the species to Kutzing ; Heiberg, and 

 Eabenhorst, PL Eur., to Montague. 



Kiitz. Bac, p. 52, T. xxviii., fig. 5, and T. xxix., fig. 84. 

 Wm. Sm., B. D., Yol. ii., p. 53, PI. xlix., fig. 327. Ealfs, in Priteh., 

 p. 815, PI. ii., fig. 45. Eab. PI. 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 macuJata, (Wm. Sm.) Marine. 



Frustules globose, distinctly punctate ; piincta divided by radiate 

 bands of a deeper colour, which latter clo not reach the centre. 

 Yalves having a distinct umbilicus. (PL 26, fig. 5a.) 



Wm. Sm., B.D., Yol. ii., p. 54, PL xlix., fig. 328. Ealfs, in 

 Priteh., p. 815. Eab. Fl. Eur., p. 37. 



Sea weeds, Bannow. Salt,clitch, near Wexford. Arran Islands, 

 Stomachs of Ascidians, Eoundstone Bay, Co. Galway. 



Genus lY. Oethosiea, 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 distinguisliing 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 



