362 Proceedings of the Eoyal Iriiih Academy. 



been identified, "were it not that authentic specimens were seen by 

 Wni. Smith, who considers it identical with his I^avicnla patula^ 

 E.D., Yol. i., p. 49, PI. xvi., fig. 139. Ealfs, in Pritch., p. 905. Eab. 

 Stissw. Diat., p. 38, T. vi., fig. 61. If in this case the figure be cor- 

 rect, it can scarcely be identified with J^avicula latiuscula, Kiitz. 

 Grunow, Yerhand. der K. K. Zool. Pot. Gesell., Pand x., 1860, p. 534,. 

 T. iv., fig. 38. Donkin, '^. H., Erit. Diat., p. 27, PL iv., fig. 7. Eab. 

 M. Eur. Alg., sect; i., p. 182. 



Lough Corrib, Co. Galway. Killurin, Co. "Wexford. iN'ewtown- 

 limayady, Co. Derry. Preaches, JSTewcastle, Co. Wicklow. 



Navicula larTceriana, ]N". S. Marine. 



Yalre linear, elliptical, gradually attenuated towards the producecF 

 ends ; stride linear, fine, close, distinctly radiate ; inteiTaedlate free- 

 space wide, greatly expanded in the middle ; median terminating to- 

 wards the central nodule in elongated expansions; length -0052, 

 breadth -0014. 



This form might be easily confounded with JS'avicula latiuscula, 

 from which it differs in the following features : the intermediate free- 

 space is much wider, the ends are produced, and the striae are radiate,., 

 and somewhat coarser. (Plate 31, fig. 16.) 



On sea-weeds, Dalkey, Co. Dublin. Preaches near iN'ewcastle, Co.. 

 Wicklow. In both these gatherings there was a considerable admix- 

 ture of fresh water forms ; the maiine forms, however, greatly prepon- 

 derated. 



Navimla grunovii, (O'Meara). Fresh or brackish water. 



Yalre broadly elliptical, longitudinal, marginal sulci very distinct ;: 

 intermediate free space wide, lanceolate, greatly expanded in the mid- 

 dle ; median line slightly undulate ; striae fine, slightly radiate ; 

 length -0040, breadth -0016. (Plate 31, fig. 17.) 



J^avicula elegans, Grunow, Yerhand. der K. K. Zool. Pot. Gesell., 

 Pand X., 1860, p. 534, T. ir., fig. 37. This author confounds this 

 form with jSTavicula elegans, Wm. Sm., of which he states he had 

 never seen a specimen ; and suggests that in case it should prove to bo 

 different from the last-named species it should be designated JS'avicula 

 lacustris. Cleve, in his Diatoms of the Ai'ctic Sea, p. 17, perceiving 

 that the form was obviously distinct fi'om jS«"avicula elegans, adopts 

 Grunow's alternative designation, which, however, must be aban- 

 doned, as the name had been applied by Gregory to designate a very 

 different form. Grunow found this species in fi-esh water as well as 

 in slightly brackish water, so that there is a difficulty in ascertaining 

 the habitat. I cannot clear up this difficulty, inasmiieh as the only 

 gathering in which the f oim oecuiTcd to me contained both marine and, 

 fresh water forms. 



Pellarena, Co. Derry. 



