328 Proceedings of the Royal Irish Academy. 



bability, tliis is identical with tlie form described by Greville, Q. J. M. S., 

 October, 1862, p. 235, PI. x., fig. 11 ; although that author remarks 

 that in his form the striae were much more obscure than in the form 

 figui'ed by Smith as above. -• 



Lough Corrib, Co. Galway, mixed with the typical form. 



Ifastogloia grevillii^ (Wm. Sm.) Fresh water. 



Valve linear ; cuneate at the obtuse extremities ; marginal plate 

 nearly linear on the inner margin, suddenly attenuated towards the 

 ends ; loculi numerous ; strise fine, linear, radiate, shortened at the 

 central nodule, so as to give a staiu'o-form appearance to the valve, 



"Wm. Sm. B. D. Yol. ii., p. 64, Supp. PI. Ixii, fig. 389. Ealfs, in 

 Pritch., p. 925, Grunow, Verhand, der K. K. Zool, Bot. Gesel., 

 Band x., 1860, p. 575. Heiberg, De Danske Diat., p. 94. Eab. PI. 

 Eur., sect. 1, p. 260. 



Kilcool, Co. "Wicklow. Lough IS'eagh, Co. Antrim. Ballyshannon, 

 Co. Donegal. Carrickhugh, Co. Derry. 



Ifastogloia costata, JS". S. Fresh water. 



Yalve linear; cuneate at ends ; length -0013, breadth -0005 ; mar- 

 ginal plates broad, on inner margin perfectly linear till near the ends, 

 where they very slightly expand, in shape of a spear head ; loculi 

 numerous ; striae strongly costate, converging in the middle, and for 

 the rest radiate ; shortened at the central nodule. (PL 29, fig. 13.) 



In shape and size, this form is so like jVIastogloia grevillii that it 

 might easily be confounded with it ; but, however, on closer investi- 

 gation it will appear quite distinct. In 11. grevillii, the fine linear 

 striae can by proper focusing be easily seen along with the loculi of 

 the marginal plate. In the present species, either fi-om the convexity 

 of the valve, or the coarseness and closeness of the costate striae, or 

 perhaps owing to both these circumstances, the plates are not easily 

 detected, except at the inner margin, where their boundary may be 

 detected by the clear intervening space into which the ends of the 

 strong costae are seen to project. 



On a moist rock, Ballyshannon, Co. Donegal. 



Genus II. Dickieia, Berkeley. 



Prond flat, leaf -like ; unbranched ; frustulcs scattered without re- 

 gular arrangement. 



Smith attributes this genus to Ealfs ; but EaKs Hmself ascribes it 

 to Berkeley, It is adopted by Kiitzing, Smith, Grunow, and Eaben- 



