24 0. NORDGAARD, [2nd ARC. EXP. fram 



named locality. One of the specimens consisted of a single stem, 

 11 mm. in height, the lower portion of which was round, with a diam. 

 of 1.5 mm. The other was a fragment (14 mm. in length) with flat- 

 tened branches, and forked at the point. This variety has hitherto only 

 been known from the St. Lawrence (Hincks) and from the above-named 

 Station in the 2nd Fram Expedition. 



41. Porella plana, Hincks. 



PI. Ill, fig.^39. 



1888. Porella skenei, f. plana, Hincks, Ann. Mag. Nat. Hist, ser. 6, vol. 1, p. 221, 



PI. 14, fig. 6. 

 1900. Porella plana, Waters, Journ. Linn. Soc, vol. 28, PI. 11, figs. 11 — 13. 

 1902. Porella plana, K. A. Ahdersson, Zool. Jahrb., vol. 16, p. 543. 



July 31, 1900, the winter haven. 



A free-growing, compressed, and higly calcified Porella from the 

 above-named locality proved to be of this species. The colony was 

 about 2 cm. in height, with a distance of 2.5 cm. between the extreme 

 points of the branches. The zocecia exactly resembled those figured by 

 Hincks (1. c, PI. 14, fig. 6). The arrangement of the avicularia was 

 also the same as that given by Hincks, there being one central and two 

 lateral. The surface of the zooecia was granulated, and there were mar- 

 ginal pores in the frontal wall (cf. Waters, 1. c, fig. 13). The opercu- 

 lum, on the other hand, (fig. 39) was cut off rather straighter than 

 Waters has represented it. 



42. Porella concinna, Busk. 

 Syn. BiDENKAp Kat., p. 22. 



Aug., 1900, the north side of N. Devon, incrusting stones; July 22, 

 1900, the winter haven, 30 fath. ; July 8, 1901, Ren Bay. 



There seems to be some difference between the boreal and the 

 arctic forms of this species; but the difference is scarcely so great as 

 to allow of a separation. 



In the arctic forms there were also large marginal pores, and the 

 oral denticle was rather narrow. In some specimens from Ren Bay, 

 the ooecia were more elongated than they have been in colonies that I 

 have seen from more southern latitudes. 



43. Porella acutirostris, Smitt. 



Syn. BiDENKAP Kat., p. 22. 



July 22, 1900, the winter haven, about 30 fath., incrusting stones; 

 July 12, 1901, bay at Land's End. 



