290 Froceedings of the Royal Irish Academy. 



very narrow. This species is very much, larger than the species here- 

 tofore described. 



Ealfs_, in Pritch., p. 790. Eab. Fl. Eur., sect. 1, p. 124.— Denti- 

 cula marina, Gregory, Diat. of Clyde, p. 24, PI. x., fig. 39. 



From stomachs of Ascidians, Roundstone Bay, Co. Galway. Sea- 

 weeds, near the Newtownlimavady junction, Co, Derry. 



Genus V. Plagiogeamma, Grev. 



Prustules similar to those of the preceding genus, from which they 

 are distinguished by the presence of a pair of strong, transverse costse, 

 including a central unstriate band. Some of the species have also, 

 besides, a similar terminal costa at either end, the space between 

 which and the apex is unstriate ; valves striate, except at the central 

 and terminal portions referred to ; striae sometimes interrupted in the 

 middle, sometimes persistent ; filaments short. 



Plagiogramnia staurophorum, (Greg.) Marine. 



Yalves furnished with a central pair of transverse, pervious costse ; 

 on front view margin slightly dilated ; on side view elliptical, obtuse ; 

 strise fine, moniliform, persistent ; central costse infiexed ; the unstri- 

 ate band bounded by the same, narrow, and extending across the valve, 

 from margin to margin. 



Heiberg, De Danske Diat., p. 165. Cleve, Om Svenska och Norska 

 Diat., p. 219. — Denticula staiu'ophora, Gregory, Diat. of Clyde, p. 24, 

 PI. X., fig. 37. Plagiogramma Gregorianun, Grev., Q. J. M. S., July, 

 1859, p. 208, PL X., figs. 1 and 2. Ealfs, in Pritch., p. 774. Eab. 

 PL Eui\, sect. 1, p. 117. 



On piles of wooden bridge, Dollymount, Oyster beds, ITalahide, 

 Co. Dublin. Sea-weeds, near l^ewtownlimavady junction, Co. Derry. 

 Sea-weeds, Bannow, Co. "Wexford. Prom stomachs of Ascidians, 

 Eoundstone Bay, Co. Galway. 



- Plagiogramma costatum, (O'M.) Marine. 



Valves furnished with both a central pair of costse and a single 

 costa at either end ; frustules in front view quadrangular ; terminal 

 constriction slight ; on side view central and terminal costse infiexed; 

 valve broadly elliptical, with slightly- cuneate ends ; central unstriate 

 band extending across the valve ; stiiae costate ; costae pervious. (PI. 

 27, fig. 20.) 



O'Meara, Q. J. M. S., April, 1869, p. 150, PI. xii., fig. 2. 



Arran Islands, Co. Galway. 



