O'Meara — Report on tJie Irish Diafomacece. 261 



Coscinodiscus stellaris, (Eoper.) Marine. 



Central rosette, consisting of five or six long and narro"w cellules ;: 

 striae extremely minute, punctate, radiate. 



Eoper, a. J. M. S., Yol. yi., p. 21, PI. iii., fig, 3. Ealfs, inPritcli., 

 828, PI. y., fig. 83. 



Oyster Shells, Dublin Bay. 



Coscinodiscus concinnus, ("\Ym. Sm.) Marine. 



Central rosette, consisting of from three to eight large flattened 

 cellules. Cellules small, radiate ; yalve divided into compartments by 

 radiating lines, which do not reach the margin, 



Wm. Sm., B. D., Yol. ii., p. 84. Eoper, Q. J. M. S., Yol. vl., p. 20, 

 PI. iii., fig. 12. Ealfs, in Pritch., p. 828. Eoper, as above cited, statesthat 

 " the larger specimens show plainly a point that is not easily discernible 

 in those under '004'^ in. diameter, namely a submarginal row of minute 

 spines, varying fi'om -jj-uVoth to ^oVoth of an inch apart, according 

 to the size of the disk, and from each of which there is a radiating 

 line almost to the centre of the valve." I have, in consequence, con- 

 siderable hesitation in including the species under the genus Coscino- 

 discus ; but, as the specimens that came under my notice were few in 

 number, and in every case imperfect, I would not presume to make 

 any change in the position to which it has been assigned. 



It was found by Wm. Sm. in Kinsale Bay, and fragments have 

 occurred on sea-weeds, Ballybrack, and on oyster-shells from Dublin 

 Bay, both in the County Dublin. 



(b). Disk ivitli a central hyaline space like a f erf oration. 



Coscinodiscus per for atus, (Ehr.) Marine. 



Hyaline centre, small, surrounded by about five rounded cellules.. 

 Cellules large, indistinctly hexagonal, radiate, decreasing in size near 

 the margin. (PI. 26, fig 20.) 



Smith describes the cellules as "equal," and EaKs as "minute;" 

 but in my specimens they differ as stated above. 



Ehr. Mic, T. xviii., fig. 46. Wm. Sm., B. D., Yol. ii., p. 85. 

 Ealfs, in Pritch., p. 829. 



Prom stomachs of Howth Oysters, Tide-pool, Monkstown, Dalkey, 

 Ballybrack ; on Oyster shells, Dublin Bay. Stomachs of Ascidians,. 

 BeKast Bay. 



(c). Dish ivithout a central rosette or vacant space. Cellules radiate. 



Coscinodiscus gig as, (Ehr.) Marine. 



Disk very large, cellules not very large, hexagonal, radiate, smaller 

 towards the centre. (PL 26, fig. 21). 



Ehr. Mic, T. xviii., fig. 34. Kiitz. Bac, p. 132, T. i., fig. 16. 



Stomachs of Ascidians, dredged on the coast of County Clare. 



