278 Proceedings of the Royal Irish Academy. 
Triceratium alternans, (Bailey.) Marine. 
Sides nearly straight; striation areolate; areoles small, roundish ; 
radiating towards the three angles; bases of the processes marked by 
what seem well defined cost. (PI. 27, fig. 11.) 
Bailey, Mic. Observations made in Sth. Carolina, Smithsonian Con- 
tributions, Vol. ii., p.40. Brightwell, Q. J. M. 8., Vol.i., p. 251, 
El vi., fig. 19. Wm.Sm., B.D., Vol. i5-p.. 26, Plog, dies45:0 Sump: 
PliSxxx:; fige§45.. Ralfs, in. Pritchs p.854)) Bloveie 20 Rab: 
Fl.- Eur. sect. 1, p. 316. 
Mud of River Liffey, Co. Dublin. 
Triceratium amblyoceros, (Ehr.) Marine. 
Sides convex ; angles broadly rounded off ; cellules radiate, distant, 
roundish ; more deeply shaded at the borders. (Pl. 27, fig. 12.) 
Ebr. Mic.;) T..xvii., fig. 1. Brichtwell Qe). Man... Violuer 
p: 250, Pl. av., fig. 14. \Ralfs; in Prteh:,, p. 857. 
Stomachs of Poolbeg oysters. Dublin Bay. 
Triceratium exiguum, (Wm. Sm.) Fresh water. 
Valve very minute; areoles minute; angles elongated; sides in- 
flexed. (Pl. 27, fig. 13.) 
Wm. Sm., B. D., Vol.i., p. 87. . Brightwell, Q. J. M. S:j- 1856, 
p. 274, Pl: xyu., fig. 1. - Ralfscin:Pritch,,. ps 8o/,..2). yar, seoele. 
River Liffey, Co. Dublin. 
Genus III. Trrvacria, Heiberg. 
Frustules normally triangular; processes springing from the sur- 
face at a right angle, and surmounted by two curved spines; transverse 
section of the processes triangular. 
Trinacria regina, (Heiberg.) Marine. 
As but one specimen of this species has been met with by me, and 
that mounted in balsam, instead of giving my own diagnosis I 
consider it better to transcribe the exhaustive description of Heiberg. 
‘Outline of the basal-surface triangular, with an extended de- 
pression towards the centre and the short pointed angles. The out- 
line of the side view less than that of the basal-surface, its sides 
bulged in the middle, and evenly depressed on both sides of the same. 
The side-surface separated from the front surface by a thick projecting 
border. The end-processes of varying height, with a prominent keel 
on the outer margin; spines slightly crescentic. The portion of the 
side-surface lying between the processes at the angles forms a gently 
elevated ridge, which again has a slight depression towards the middle 
