624 Scientific Proceedings, Royal Dublin Society. 



seen on the lower surface, and in the absence of intermediate cells. 

 The inclusion of S. simplex within the genus Stichopora requires 

 a modification of the definition of the genus, since the cells in this 

 species are arranged in radiating series, with the interpolation of 

 other series towards the periphery. 



The fertile zooecia, with their ooecia, occupy an area about 

 twice the size of the others ; the operculum is broadened out, at 

 the expense of the length, the pressing out of the lateral margins 

 leaving the muscle marks more plainly visible (see figure). 



Barentsia laxa, n. sp. 

 (PL xvii., fig. 6.) 



Polypides arising from a jointed, creeping stolon. 



Expanded basal portion of pedicels plain and unmarked ; 

 pedicels cylindrical and chitinous below, membranous above and 

 attached to the polypide directly, and without the intervention 

 of a fleshy peduncle. 



Polypides large and gibbous. 



Measurements. — Total length, 3 mm. Length of ' barrel ' por- 

 tion (including the superior conical part), '25 mm. Breadth of 

 barrel, "16 mm. Polypide, *35 to - 4 mm. in breadth ; '4 to *5 mm- 

 in height. 



Habitat. — Station 4 ; growing over Flustra cribriformis. 



The new species resembles, in several particulars, Barentsia 

 major, Hincks, 1 from the St. Lawrence, but differs from the latter 

 in manner of attachment of the polypide to the pedicle. B. laxa is 

 without the fleshy stalk, which Mr. Hincks refers to as a distinct 

 feature in his species. 



Barentsia discreta, Busk, is considerably larger ; the barrel is 

 marked with broad annulations, and the pedicle is chitinous 

 throughout, and marked with funnel-shaped pits. 



1 Hincks, Ann. Mag. Nat. Hist. (6) i. 1888, pp. 226, PI. XV. fig. 2. 



