PORINA TUBULOSA. 231 



below, smooth, punctured with small stellate pores; 

 above, produced iuto a long, tubular neck, which stands 

 erect, surface entire, with a circular orifice and thin 

 peristome, which is armed in the young state with two 

 or four spines ; on the lower part of the neck a large 

 projecting tubular pore. Ocecia arcuate, shallow, set 

 very far back behind the tubular peristome, smooth, 

 with a few perforations. 



Range of Variation. The cylindrical prolongation of the 

 cell varies considerably in length. This is partly de- 

 pendent upon age ; and in marginal cells the erect portion 

 and the pore, which is placed upon it, are wanting alto- 

 gether. Apart from this, however, colonies differ very 

 much in the degree in which the neck is developed. In 

 specimens from Greenland and the Gulf of St. Lawrence 

 it is a much less striking feature than in British ex- 

 amples. 



Habitat. On stones, shells, Algae, &c., from the littoral 

 region to deep water. 



Localities. Shetland ; " on a stone dredged in a few 

 fathoms water at Hillswick " (A. M. N.) : Wick, between 

 tide-mai'ks (C. W. P.). 



Geographical Distribution. Spitzbergeu, not com- 

 mon, on Algse, Ascidians, shells, from the littoral region to 

 30-50 fathoms (Smitt) : off Frederickshaab, Davis Straits, 

 100 fathoms (Wallich) : off Bear Island (Dutch Arctic 

 Exped.) : Gulf of St. Lawrence (Dr. Dawson). 



Range in Time. Scotch Glacial deposits (Geikie) : 

 Paleolithic (A. Bell). 



In this well-marked form the oral spines are commonly 

 wanting, and are only to be met with on the edge of the 

 colony. The ovicell is placed very far back ; and the 

 cylindrical portion of the cell rises in front of it. The 

 pore is situated at the base of the neck, close to the June- 



