O'Meara — Rejyort on the Irhli Diatomacca\ 327 



Mastogloia apicidata, (Wm. Sm.) Marine. 



Valves broadly elliptical ; slightly produced at the ends ; median 

 line fine, with two sulci, one at either side, and very close to it ; 

 parallel for greater part of length, and converging towards the ends ; 

 central nodule small ; marginal plates narrow, gradually attenuated 

 towards the ends, where they suddenly decrease in breadth ; loculi 

 numerous ; space between the inner margins broadly elliptical, and 

 slightly expanded at the ends ; strise fine, closely punctate, slightly 

 radiate. 



Wm. Sm., B. D. Vol. ii., p. 65. Supp. PI. Ixii., fig. 387. Ealfs, 

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

 Band x., 1860, p. 577, T. vii., fig. 9. Eab. PL Eur., sect. l,p. 262. 



DoUymount Strand, Co. Dublin. Stomachs of Ascidians, Eound- 

 stone Bay, Co. Galway. 



Mastogloia smithii, (Thwaites.) Presh or brackish water. 



Valves elliptical ; frequently produced at the ends ; marginal plates 

 relatively broad ; attenuated at the ends ; space included between the 

 inner margins narrow ; slightly expanded at the ends ; stria) fine,, 

 linear; slightly radiate. (PL 29, fig. 12.) 



This form varies greatly in size and shape, as well as in the habitat. 

 It seems essentially a fresh water form, for I have found it frequently 

 in localities far remote from mariae infiuences ; and also in places 

 where, so far as I could judge, there was no likelihood of mixture of 

 fresh water with the salt. Under the circumstances, I was anxioua 

 to submit the forms to the most rigid examination, but could detect 

 no specific difference between them. Grunow observes that, in the 

 specimen that came under his notice, there was even a tolerably wide 

 transversely expanded central nodule, which he considers should be 

 established as the characteristic distinction between this species and 

 Mastogloia lanceolata. I may mention that this feature, though 

 frequently noticeable, is not of univei'sal occurrence. 



Wm. Sm., B.D., Vol. ii., p. 65, PL liv., fig. 341. Ealfs, in Pritc;h., 

 p. 925. Grunow, Verhand. der K. K. Zool. Bot. Gesel., Band x., 1860, 

 p. 575, T. \-ii., fig. 11. Eab. PL Eur., sect. 1, p. 261. Cleve, Om 

 Svenska och Norska Diat., p. 230. 



Tacumshane, Co. "Wexford. Lough Gill, Co. Kerry. Kilcool, 

 Co. Wicklow. !N"ewtownlimavady, Co. Derry. In all which gatherings 

 there was a mixture of fresh and brackish forms. Tide pool, Greystones, 

 Co. Wicklow, where the forms were mostly marine. Lough Corrib, 

 Co. Galway, wholly free from marine influence. 



Var. capitata, (Wm. Sm.) Fresh water. 



Agreeing with the typical form, only that the produced ends are 

 capitate ; the stride, also, which are similarly arranged, may easily be 

 resolved into minute dots. 



Wm. Sm., B. D., Vol. ii., p. 6.', PL liv., fig. Cil b. In all pro- 



