9 8 



HYDROIDA 11 



siderable elasticity in respect of physical conditions. The chief occurrence of the species falls in the 

 lower part of the littoral region and the upper part of the abyssal. 



Sertularella tricuspidata (Alder) Hincks. 

 1856 Sertularia tricuspidata, Alder, A notice of some new genera and species, p. 356, pi. 13, figs. 1 — 2. 

 1868 Sertularella tricuspidata, Hincks, A History of the British Hydroid Zoophytes, p. 239, pi. 47, fig. 1. 



Upright colonies with pinnate or quite irregularly bushy ramification ; in the pinnate colonies, 

 the branches are alternating or subalternating, not infrequently they may themselves be dichotomi- 

 cally or pinnately branched ; the branches are often bent or twisted. The monosiphonic stem and 

 branches are segmented; each internodium has a hydrotheca. The hydrotheca; are situate on the 

 distal part of the internodium, and are cylindrical or slightly barrel-shaped, with their narrowest part 

 immediately below the aperture; they have three teeth of equal size on the aperture margin, the one 

 median adcauline; in the sinuses between the teeth, the three triangular plates of the closing apparatus 

 are attached. The adcauline wall of the hydrotheca has a free distal part between half and two-thirds 

 the length of the hydrotheca. The polyp has a well-developed abcauline blind sack. 



The gouothecse are attached under the base of the hydrotheca;. They are oval to pear-shaped, 

 with a short and narrow, reversedly conical, distally central neck, and with deep transverse furrows. 



Material : 



"Ingolf", beach of Jan Mayen. 



— St. 3 63°35 r N., io°24' W., depth 272 fathoms 0,5° 



- 34 65*17' N., 54*17' W, 55 



- 54 63*08' N, 15*40' W, 691 3,9° 



- 87 65*02,3' N., 23*56,2 W., - no 



- 95 65*14' N., 30*39' W., 752 2,1° 

 "Thor" 65°52' N., 23°58' W., — 62 metres 



65*29,5' N., 2 4 °6 3 ' W, - 40 - 

 64*02' N., 22*33' W., - 34 ■ — 

 63°3o' N., 2o°i4' W., - 80 — 

 Greenland: mouth of Nerak (depth not stated) 

 Hunde-Eiland ( — - — ) 

 Egedesminde, depth 30—40 fathoms 



Store Hellefiskebanke, — 24 — 



Sukkertoppen, on Boltenia (without further details) 

 Frederikshaab ( — — — ) 



Iceland: Bakkefjord, depth 25 — 32 fathoms 



Lonafjord, — 40 



Malarif (depth not stated) 



Reydarfjord, — 60 — 80 — |labelled Sertularella polyzonias] 



6 3 °2i' N, i 7 °i 5 ' W. 58 



