278 Proceedings of the Royal Irish Academy. 



Triceratium aUernans, (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 costse. (PI. 27, fig. 11.) 



Bailey, Mic. Observations made in Sth. Carolina, Smithsonian Con- 

 tributions, Yol. ii., p. 40. Brightwell, Q. J. M. S., Yol. i., p. 251, 

 PL Yi., fig. 19. Wm. Sm., B. D., Yol. i., p. 26, PI. v., fig. 45. Supp. 

 PL XXX., fig. 45. EaKs, in Pritch., p. 854, PL yi., fig. 21. Eab. 

 PL Eur. sect. 1, p. 316. 



Mud of Eiver 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.) 



Ehr. Mic, T. xviii., fig. 51. Brightwell. Q. J. M. S., Yol. i.. 

 p. 250, PL iv., fig. 14. Ealfs, in Pritch., p. 857. 



Stomachs of Poolbeg oysters. Dublin Bay. 



Triceratium exigimm, ("Wm. Sm.) Presh water. 



Yalve very minute ; areoles minute ; angles elongated ; sides ih- 

 flexed. (PL 27, fig. 13.) 



Wm. Sm., B. D., Yol. ii., p. 87. BrightweU, Q. J. M. S., 1856, 

 p. 274, PL xvii., fig. 1. Ealfs, in Pritch., p. 857, PL vL, fig. 16. 



Eiver Lrffey, Co. Dublin. 



Genus III. Tees'aceia, Heiberg. 



Prustules nonnally 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 fi'ont 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 



